Simplify string formatting (#4757)

11 files changed, 33 insertions, 33 deletions

diff --git a/src/cryptography/hazmat/backends/openssl/aead.py b/src/cryptography/hazmat/backends/openssl/aead.py
index 73195ff3..1335b4f9 100644
--- a/src/cryptography/hazmat/backends/openssl/aead.py
+++ b/src/cryptography/hazmat/backends/openssl/aead.py
@@ -18,10 +18,10 @@ def _aead_cipher_name(cipher):
     if isinstance(cipher, ChaCha20Poly1305):
         return b"chacha20-poly1305"
     elif isinstance(cipher, AESCCM):
-        return "aes-{0}-ccm".format(len(cipher._key) * 8).encode("ascii")
+        return "aes-{}-ccm".format(len(cipher._key) * 8).encode("ascii")
     else:
         assert isinstance(cipher, AESGCM)
-        return "aes-{0}-gcm".format(len(cipher._key) * 8).encode("ascii")
+        return "aes-{}-gcm".format(len(cipher._key) * 8).encode("ascii")
 
 
 def _aead_setup(backend, cipher_name, key, nonce, tag, tag_len, operation):
diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index 0a9bc53a..33a96af2 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -187,7 +187,7 @@ class Backend(object):
 
     def _evp_md_from_algorithm(self, algorithm):
         if algorithm.name == "blake2b" or algorithm.name == "blake2s":
-            alg = "{0}{1}".format(
+            alg = "{}{}".format(
                 algorithm.name, algorithm.digest_size * 8
             ).encode("ascii")
         else:
@@ -221,7 +221,7 @@ class Backend(object):
 
     def register_cipher_adapter(self, cipher_cls, mode_cls, adapter):
         if (cipher_cls, mode_cls) in self._cipher_registry:
-            raise ValueError("Duplicate registration for: {0} {1}.".format(
+            raise ValueError("Duplicate registration for: {} {}.".format(
                 cipher_cls, mode_cls)
             )
         self._cipher_registry[cipher_cls, mode_cls] = adapter
@@ -980,7 +980,7 @@ class Backend(object):
                 encode = handlers[extension.oid]
             except KeyError:
                 raise NotImplementedError(
-                    'Extension not supported: {0}'.format(extension.oid)
+                    'Extension not supported: {}'.format(extension.oid)
                 )
 
             ext_struct = encode(self, extension.value)
@@ -1244,7 +1244,7 @@ class Backend(object):
                 else:
                     assert userdata.error == -2
                     raise ValueError(
-                        "Passwords longer than {0} bytes are not supported "
+                        "Passwords longer than {} bytes are not supported "
                         "by this backend.".format(userdata.maxsize - 1)
                     )
             else:
@@ -1356,7 +1356,7 @@ class Backend(object):
             return _EllipticCurvePrivateKey(self, ec_cdata, evp_pkey)
         else:
             raise UnsupportedAlgorithm(
-                "Backend object does not support {0}.".format(curve.name),
+                "Backend object does not support {}.".format(curve.name),
                 _Reasons.UNSUPPORTED_ELLIPTIC_CURVE
             )
 
@@ -1610,7 +1610,7 @@ class Backend(object):
         curve_nid = self._lib.OBJ_sn2nid(curve_name.encode())
         if curve_nid == self._lib.NID_undef:
             raise UnsupportedAlgorithm(
-                "{0} is not a supported elliptic curve".format(curve.name),
+                "{} is not a supported elliptic curve".format(curve.name),
                 _Reasons.UNSUPPORTED_ELLIPTIC_CURVE
             )
         return curve_nid
@@ -2323,7 +2323,7 @@ class GetCipherByName(object):
 
 
 def _get_xts_cipher(backend, cipher, mode):
-    cipher_name = "aes-{0}-xts".format(cipher.key_size // 2)
+    cipher_name = "aes-{}-xts".format(cipher.key_size // 2)
     return backend._lib.EVP_get_cipherbyname(cipher_name.encode("ascii"))
 
 
diff --git a/src/cryptography/hazmat/backends/openssl/ciphers.py b/src/cryptography/hazmat/backends/openssl/ciphers.py
index 66ac5fd6..94b48f52 100644
--- a/src/cryptography/hazmat/backends/openssl/ciphers.py
+++ b/src/cryptography/hazmat/backends/openssl/ciphers.py
@@ -40,7 +40,7 @@ class _CipherContext(object):
             adapter = registry[type(cipher), type(mode)]
         except KeyError:
             raise UnsupportedAlgorithm(
-                "cipher {0} in {1} mode is not supported "
+                "cipher {} in {} mode is not supported "
                 "by this backend.".format(
                     cipher.name, mode.name if mode else mode),
                 _Reasons.UNSUPPORTED_CIPHER
@@ -53,7 +53,7 @@ class _CipherContext(object):
                 msg += "in {0.name} mode ".format(mode)
             msg += (
                 "is not supported by this backend (Your version of OpenSSL "
-                "may be too old. Current version: {0}.)"
+                "may be too old. Current version: {}.)"
             ).format(self._backend.openssl_version_text())
             raise UnsupportedAlgorithm(msg, _Reasons.UNSUPPORTED_CIPHER)
 
@@ -127,7 +127,7 @@ class _CipherContext(object):
     def update_into(self, data, buf):
         if len(buf) < (len(data) + self._block_size_bytes - 1):
             raise ValueError(
-                "buffer must be at least {0} bytes for this "
+                "buffer must be at least {} bytes for this "
                 "payload".format(len(data) + self._block_size_bytes - 1)
             )
 
@@ -207,7 +207,7 @@ class _CipherContext(object):
             )
         if len(tag) < self._mode._min_tag_length:
             raise ValueError(
-                "Authentication tag must be {0} bytes or longer.".format(
+                "Authentication tag must be {} bytes or longer.".format(
                     self._mode._min_tag_length)
             )
         res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
diff --git a/src/cryptography/hazmat/backends/openssl/decode_asn1.py b/src/cryptography/hazmat/backends/openssl/decode_asn1.py
index 007675d4..773189d4 100644
--- a/src/cryptography/hazmat/backends/openssl/decode_asn1.py
+++ b/src/cryptography/hazmat/backends/openssl/decode_asn1.py
@@ -135,7 +135,7 @@ def _decode_general_name(backend, gn):
             if "1" in bits[prefix:]:
                 raise ValueError("Invalid netmask")
 
-            ip = ipaddress.ip_network(base.exploded + u"/{0}".format(prefix))
+            ip = ipaddress.ip_network(base.exploded + u"/{}".format(prefix))
         else:
             ip = ipaddress.ip_address(data)
 
@@ -160,7 +160,7 @@ def _decode_general_name(backend, gn):
     else:
         # x400Address or ediPartyName
         raise x509.UnsupportedGeneralNameType(
-            "{0} is not a supported type".format(
+            "{} is not a supported type".format(
                 x509._GENERAL_NAMES.get(gn.type, gn.type)
             ),
             gn.type
@@ -202,7 +202,7 @@ class _X509ExtensionParser(object):
             )
             if oid in seen_oids:
                 raise x509.DuplicateExtension(
-                    "Duplicate {0} extension found".format(oid), oid
+                    "Duplicate {} extension found".format(oid), oid
                 )
 
             # These OIDs are only supported in OpenSSL 1.1.0+ but we want
@@ -245,7 +245,7 @@ class _X509ExtensionParser(object):
                 if ext_data == backend._ffi.NULL:
                     backend._consume_errors()
                     raise ValueError(
-                        "The {0} extension is invalid and can't be "
+                        "The {} extension is invalid and can't be "
                         "parsed".format(oid)
                     )
 
@@ -698,7 +698,7 @@ def _decode_crl_reason(backend, enum):
     try:
         return x509.CRLReason(_CRL_ENTRY_REASON_CODE_TO_ENUM[code])
     except KeyError:
-        raise ValueError("Unsupported reason code: {0}".format(code))
+        raise ValueError("Unsupported reason code: {}".format(code))
 
 
 def _decode_invalidity_date(backend, inv_date):
@@ -758,7 +758,7 @@ def _asn1_string_to_utf8(backend, asn1_string):
     res = backend._lib.ASN1_STRING_to_UTF8(buf, asn1_string)
     if res == -1:
         raise ValueError(
-            "Unsupported ASN1 string type. Type: {0}".format(asn1_string.type)
+            "Unsupported ASN1 string type. Type: {}".format(asn1_string.type)
         )
 
     backend.openssl_assert(buf[0] != backend._ffi.NULL)
diff --git a/src/cryptography/hazmat/backends/openssl/ec.py b/src/cryptography/hazmat/backends/openssl/ec.py
index a8d69bdf..2ca48091 100644
--- a/src/cryptography/hazmat/backends/openssl/ec.py
+++ b/src/cryptography/hazmat/backends/openssl/ec.py
@@ -62,7 +62,7 @@ def _sn_to_elliptic_curve(backend, sn):
         return ec._CURVE_TYPES[sn]()
     except KeyError:
         raise UnsupportedAlgorithm(
-            "{0} is not a supported elliptic curve".format(sn),
+            "{} is not a supported elliptic curve".format(sn),
             _Reasons.UNSUPPORTED_ELLIPTIC_CURVE
         )
 
diff --git a/src/cryptography/hazmat/backends/openssl/encode_asn1.py b/src/cryptography/hazmat/backends/openssl/encode_asn1.py
index 35575762..61cfd14d 100644
--- a/src/cryptography/hazmat/backends/openssl/encode_asn1.py
+++ b/src/cryptography/hazmat/backends/openssl/encode_asn1.py
@@ -475,7 +475,7 @@ def _encode_general_name(backend, name):
         gn.d.uniformResourceIdentifier = asn1_str
     else:
         raise ValueError(
-            "{0} is an unknown GeneralName type".format(name)
+            "{} is an unknown GeneralName type".format(name)
         )
 
     return gn
diff --git a/src/cryptography/hazmat/backends/openssl/hashes.py b/src/cryptography/hazmat/backends/openssl/hashes.py
index 549fa2bf..7f9d840b 100644
--- a/src/cryptography/hazmat/backends/openssl/hashes.py
+++ b/src/cryptography/hazmat/backends/openssl/hashes.py
@@ -25,7 +25,7 @@ class _HashContext(object):
             evp_md = self._backend._evp_md_from_algorithm(algorithm)
             if evp_md == self._backend._ffi.NULL:
                 raise UnsupportedAlgorithm(
-                    "{0} is not a supported hash on this backend.".format(
+                    "{} is not a supported hash on this backend.".format(
                         algorithm.name),
                     _Reasons.UNSUPPORTED_HASH
                 )
diff --git a/src/cryptography/hazmat/backends/openssl/hmac.py b/src/cryptography/hazmat/backends/openssl/hmac.py
index b23ac649..4b66a610 100644
--- a/src/cryptography/hazmat/backends/openssl/hmac.py
+++ b/src/cryptography/hazmat/backends/openssl/hmac.py
@@ -28,7 +28,7 @@ class _HMACContext(object):
             evp_md = self._backend._evp_md_from_algorithm(algorithm)
             if evp_md == self._backend._ffi.NULL:
                 raise UnsupportedAlgorithm(
-                    "{0} is not a supported hash on this backend".format(
+                    "{} is not a supported hash on this backend".format(
                         algorithm.name),
                     _Reasons.UNSUPPORTED_HASH
                 )
diff --git a/src/cryptography/hazmat/backends/openssl/ocsp.py b/src/cryptography/hazmat/backends/openssl/ocsp.py
index 16dbbc2a..7420f657 100644
--- a/src/cryptography/hazmat/backends/openssl/ocsp.py
+++ b/src/cryptography/hazmat/backends/openssl/ocsp.py
@@ -82,7 +82,7 @@ def _hash_algorithm(backend, cert_id):
         return _OIDS_TO_HASH[oid]
     except KeyError:
         raise UnsupportedAlgorithm(
-            "Signature algorithm OID: {0} not recognized".format(oid)
+            "Signature algorithm OID: {} not recognized".format(oid)
         )
 
 
@@ -134,7 +134,7 @@ class _OCSPResponse(object):
             return x509._SIG_OIDS_TO_HASH[oid]
         except KeyError:
             raise UnsupportedAlgorithm(
-                "Signature algorithm OID:{0} not recognized".format(oid)
+                "Signature algorithm OID:{} not recognized".format(oid)
             )
 
     @property
diff --git a/src/cryptography/hazmat/backends/openssl/rsa.py b/src/cryptography/hazmat/backends/openssl/rsa.py
index 30d59bd8..3e4c2fd2 100644
--- a/src/cryptography/hazmat/backends/openssl/rsa.py
+++ b/src/cryptography/hazmat/backends/openssl/rsa.py
@@ -59,7 +59,7 @@ def _enc_dec_rsa(backend, key, data, padding):
 
     else:
         raise UnsupportedAlgorithm(
-            "{0} is not supported by this backend.".format(
+            "{} is not supported by this backend.".format(
                 padding.name
             ),
             _Reasons.UNSUPPORTED_PADDING
@@ -178,7 +178,7 @@ def _rsa_sig_determine_padding(backend, key, padding, algorithm):
         padding_enum = backend._lib.RSA_PKCS1_PSS_PADDING
     else:
         raise UnsupportedAlgorithm(
-            "{0} is not supported by this backend.".format(padding.name),
+            "{} is not supported by this backend.".format(padding.name),
             _Reasons.UNSUPPORTED_PADDING
         )
 
@@ -197,7 +197,7 @@ def _rsa_sig_setup(backend, padding, algorithm, key, data, init_func):
     if res == 0:
         backend._consume_errors()
         raise UnsupportedAlgorithm(
-            "{0} is not supported by this backend for RSA signing.".format(
+            "{} is not supported by this backend for RSA signing.".format(
                 algorithm.name
             ),
             _Reasons.UNSUPPORTED_HASH
diff --git a/src/cryptography/hazmat/backends/openssl/x509.py b/src/cryptography/hazmat/backends/openssl/x509.py
index b3eb797d..920eaf52 100644
--- a/src/cryptography/hazmat/backends/openssl/x509.py
+++ b/src/cryptography/hazmat/backends/openssl/x509.py
@@ -29,7 +29,7 @@ class _Certificate(object):
         self._x509 = x509
 
     def __repr__(self):
-        return "<Certificate(subject={0}, ...)>".format(self.subject)
+        return "<Certificate(subject={}, ...)>".format(self.subject)
 
     def __eq__(self, other):
         if not isinstance(other, x509.Certificate):
@@ -58,7 +58,7 @@ class _Certificate(object):
             return x509.Version.v3
         else:
             raise x509.InvalidVersion(
-                "{0} is not a valid X509 version".format(version), version
+                "{} is not a valid X509 version".format(version), version
             )
 
     @property
@@ -107,7 +107,7 @@ class _Certificate(object):
             return x509._SIG_OIDS_TO_HASH[oid]
         except KeyError:
             raise UnsupportedAlgorithm(
-                "Signature algorithm OID:{0} not recognized".format(oid)
+                "Signature algorithm OID:{} not recognized".format(oid)
             )
 
     @property
@@ -261,7 +261,7 @@ class _CertificateRevocationList(object):
             return x509._SIG_OIDS_TO_HASH[oid]
         except KeyError:
             raise UnsupportedAlgorithm(
-                "Signature algorithm OID:{0} not recognized".format(oid)
+                "Signature algorithm OID:{} not recognized".format(oid)
             )
 
     @property
@@ -413,7 +413,7 @@ class _CertificateSigningRequest(object):
             return x509._SIG_OIDS_TO_HASH[oid]
         except KeyError:
             raise UnsupportedAlgorithm(
-                "Signature algorithm OID:{0} not recognized".format(oid)
+                "Signature algorithm OID:{} not recognized".format(oid)
             )
 
     @property