Replaced yaml dump of Request object with plain dict dump

vcr/serializers/yamlserializer.py

@@ -1,5 +1,6 @@
-import sys
 import yaml
+
+from vcr.request import Request
 from . import compat
 
 # Use the libYAML versions if possible
@@ -21,25 +22,9 @@ Deserializing: string (yaml converts from utf-8) -> bytestring
 """
 
 
-def _restore_frozenset():
-    """
-    Restore __builtin__.frozenset for cassettes serialized in python2 but
-    deserialized in python3 and builtins.frozenset for cassettes serialized
-    in python3 and deserialized in python2
-    """
-
-    if '__builtin__' not in sys.modules:
-        import builtins
-        sys.modules['__builtin__'] = builtins
-
-    if 'builtins' not in sys.modules:
-        sys.modules['builtins'] = sys.modules['__builtin__']
-
-
 def deserialize(cassette_string):
-    _restore_frozenset()
     data = yaml.load(cassette_string, Loader=Loader)
-    requests = [r['request'] for r in data]
+    requests = [Request._from_dict(r['request']) for r in data]
     responses = [r['response'] for r in data]
     responses = [compat.convert_to_bytes(r['response']) for r in data]
     return requests, responses
@@ -47,7 +32,7 @@ def deserialize(cassette_string):
 
 def serialize(cassette_dict):
     data = ([{
-        'request': request,
+        'request': request._to_dict(),
         'response': response,
     } for request, response in zip(
         cassette_dict['requests'],