README example generation now failing

[jonahbenton]

>>> import swaggerconformance
>>> client = swaggerconformance.client.Client('http://petstore.swagger.io/v2/swagger.json')
No success responses defined - allowing 200
No success responses defined - allowing 200
No success responses defined - allowing 200
No success responses defined - allowing 200
No success responses defined - allowing 200
Only 'default' response defined - allowing any 2XX
Only 'default' response defined - allowing any 2XX
No success responses defined - allowing 200
No success responses defined - allowing 200
Only 'default' response defined - allowing any 2XX
Only 'default' response defined - allowing any 2XX
>>> strategy_factory = swaggerconformance.strategies.StrategyFactory()
>>> operation = client.api.endpoints["/pet"]["put"]
>>> strategy = operation.parameters_strategy(strategy_factory)
>>> strategy.example()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 315, in example
    example_generating_inner_function()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 303, in example_generating_inner_function
    @settings(
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/core.py", line 975, in wrapped_test
    wrapped_test, arguments, kwargs, given_kwargs, argspec, settings,
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/core.py", line 415, in process_arguments_to_given
    search_strategy.validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 378, in validate
    self.do_validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/collections.py", line 39, in do_validate
    s.validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 378, in validate
    self.do_validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 646, in do_validate
    self.mapped_strategy.validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 378, in validate
    self.do_validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 118, in do_validate
    w.validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 378, in validate
    self.do_validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 646, in do_validate
    self.mapped_strategy.validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 378, in validate
    self.do_validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/collections.py", line 39, in do_validate
    s.validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/strategies.py", line 378, in validate
    self.do_validate()
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 116, in do_validate
    w = self.wrapped_strategy
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 101, in wrapped_strategy
    unwrapped_args = tuple(unwrap_strategies(s) for s in self.__args)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 101, in <genexpr>
    unwrapped_args = tuple(unwrap_strategies(s) for s in self.__args)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 45, in unwrap_strategies
    result = unwrap_strategies(s.wrapped_strategy)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 101, in wrapped_strategy
    unwrapped_args = tuple(unwrap_strategies(s) for s in self.__args)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 101, in <genexpr>
    unwrapped_args = tuple(unwrap_strategies(s) for s in self.__args)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 45, in unwrap_strategies
    result = unwrap_strategies(s.wrapped_strategy)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 101, in wrapped_strategy
    unwrapped_args = tuple(unwrap_strategies(s) for s in self.__args)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 101, in <genexpr>
    unwrapped_args = tuple(unwrap_strategies(s) for s in self.__args)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 45, in unwrap_strategies
    result = unwrap_strategies(s.wrapped_strategy)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/lazy.py", line 106, in wrapped_strategy
    base = self.function(*self.__args, **self.__kwargs)
  File "/home/jbenton/.local/share/virtualenvs/swagger-conformance-X22JbcNe/lib/python3.7/site-packages/hypothesis/strategies/_internal/core.py", line 650, in sampled_from
    raise InvalidArgument("Cannot sample from a length-zero sequence.")
hypothesis.errors.InvalidArgument: Cannot sample from a length-zero sequence.