gistfile1.txt

m = mock.Mock(name='name',
              description='desc',
              id='12345',
              enabled=True)

g = {m.name: {'description': m.description,
              'id': m.id}}
print g
print yaml.safe_dump(g, default_flow_style=False)

gistfile2.txt

{<Mock name='name.name' id='4326965456'>: {'description': 'desc', 'id': '12345'}}
Traceback (most recent call last):
  File "test.py", line 17, in <module>
    print yaml.safe_dump(m, default_flow_style=False)
  File "/Library/Python/2.7/site-packages/yaml/__init__.py", line 218, in safe_dump
    return dump_all([data], stream, Dumper=SafeDumper, **kwds)
  File "/Library/Python/2.7/site-packages/yaml/__init__.py", line 190, in dump_all
    dumper.represent(data)
  File "/Library/Python/2.7/site-packages/yaml/representer.py", line 28, in represent
    node = self.represent_data(data)
  File "/Library/Python/2.7/site-packages/yaml/representer.py", line 67, in represent_data
    node = self.yaml_representers[None](self, data)
  File "/Library/Python/2.7/site-packages/yaml/representer.py", line 247, in represent_undefined
    raise RepresenterError("cannot represent an object: %s" % data)
yaml.representer.RepresenterError: cannot represent an object: <Mock name='name' id='4326915920'>

gistfile3.txt

m = mock.Mock(shit='name',
              description='desc',
              id='12345',
              enabled=True)

g = {m.shit: {'description': m.description,
              'id': m.id}}
print g
print yaml.safe_dump(g, default_flow_style=False)

gistfile4.txt

{'name': {'description': 'desc', 'id': '12345'}}
name:
  description: desc
  id: '12345'

Stumbled across blog where the comments suggest using mock.configure_mock(). Works great.