Remove elifs and replace with else + assert

This is kind of ugly, but resolves many partial branch coverage issues.

3 files changed, 18 insertions, 10 deletions

diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index db4f963a..5ab46d44 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -1577,13 +1577,15 @@ class Backend(object):
             if format is serialization.PrivateFormat.PKCS8:
                 write_bio = self._lib.PEM_write_bio_PKCS8PrivateKey
                 key = evp_pkey
-            elif format is serialization.PrivateFormat.TraditionalOpenSSL:
+            else:
+                assert format is serialization.PrivateFormat.TraditionalOpenSSL
                 if evp_pkey.type == self._lib.EVP_PKEY_RSA:
                     write_bio = self._lib.PEM_write_bio_RSAPrivateKey
                 elif evp_pkey.type == self._lib.EVP_PKEY_DSA:
                     write_bio = self._lib.PEM_write_bio_DSAPrivateKey
-                elif (self._lib.Cryptography_HAS_EC == 1 and
-                      evp_pkey.type == self._lib.EVP_PKEY_EC):
+                else:
+                    assert self._lib.Cryptography_HAS_EC == 1
+                    assert evp_pkey.type == self._lib.EVP_PKEY_EC
                     write_bio = self._lib.PEM_write_bio_ECPrivateKey
 
                 key = cdata
@@ -1600,7 +1602,8 @@ class Backend(object):
                 return self._private_key_bytes_traditional_der(
                     evp_pkey.type, cdata
                 )
-            elif format is serialization.PrivateFormat.PKCS8:
+            else:
+                assert format is serialization.PrivateFormat.PKCS8
                 write_bio = self._lib.i2d_PKCS8PrivateKey_bio
                 key = evp_pkey
         else:
@@ -1625,7 +1628,8 @@ class Backend(object):
         elif (self._lib.Cryptography_HAS_EC == 1 and
               key_type == self._lib.EVP_PKEY_EC):
             write_bio = self._lib.i2d_ECPrivateKey_bio
-        elif key_type == self._lib.EVP_PKEY_DSA:
+        else:
+            assert key_type == self._lib.EVP_PKEY_DSA
             write_bio = self._lib.i2d_DSAPrivateKey_bio
 
         bio = self._create_mem_bio()
@@ -1640,7 +1644,8 @@ class Backend(object):
         if format is serialization.PublicFormat.SubjectPublicKeyInfo:
             if encoding is serialization.Encoding.PEM:
                 write_bio = self._lib.PEM_write_bio_PUBKEY
-            elif encoding is serialization.Encoding.DER:
+            else:
+                assert encoding is serialization.Encoding.DER
                 write_bio = self._lib.i2d_PUBKEY_bio
 
             key = evp_pkey
@@ -1649,7 +1654,8 @@ class Backend(object):
             assert evp_pkey.type == self._lib.EVP_PKEY_RSA
             if encoding is serialization.Encoding.PEM:
                 write_bio = self._lib.PEM_write_bio_RSAPublicKey
-            elif encoding is serialization.Encoding.DER:
+            else:
+                assert encoding is serialization.Encoding.DER
                 write_bio = self._lib.i2d_RSAPublicKey_bio
 
             key = cdata
diff --git a/src/cryptography/hazmat/backends/openssl/rsa.py b/src/cryptography/hazmat/backends/openssl/rsa.py
index 21414c05..822c7304 100644
--- a/src/cryptography/hazmat/backends/openssl/rsa.py
+++ b/src/cryptography/hazmat/backends/openssl/rsa.py
@@ -268,8 +268,9 @@ class _RSASignatureContext(object):
                     self._backend._lib.RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE):
                 reason = ("Salt length too long for key size. Try using "
                           "MAX_LENGTH instead.")
-            elif (errors[0].reason ==
-                    self._backend._lib.RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY):
+            else:
+                assert (errors[0].reason ==
+                        self._backend._lib.RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY)
                 reason = "Digest too large for key size. Use a larger key."
             assert reason is not None
             raise ValueError(reason)
diff --git a/src/cryptography/hazmat/backends/openssl/x509.py b/src/cryptography/hazmat/backends/openssl/x509.py
index 493abc83..e7a9a792 100644
--- a/src/cryptography/hazmat/backends/openssl/x509.py
+++ b/src/cryptography/hazmat/backends/openssl/x509.py
@@ -386,7 +386,8 @@ def _decode_certificate_policies(backend, ext):
                         pqi.d.cpsuri.data, pqi.d.cpsuri.length
                     )[:].decode('ascii')
                     qualifiers.append(cpsuri)
-                elif pqualid == x509.OID_CPS_USER_NOTICE:
+                else:
+                    assert pqualid == x509.OID_CPS_USER_NOTICE
                     user_notice = _decode_user_notice(
                         backend, pqi.d.usernotice
                     )