APIs with captures are rendered to syntactically invalid Python

[exarkun]

Part of the test suite which is commented out fails now if tweaked slightly to fix a type error:

    it "should build urls properly with / separator" $ do
      let pyUrl = makePyUrl customOptions (UnTypedPythonRequest req) " "
      pyUrl `shouldBe` "\"urlForRequesting:9000/login-with-path-var-and-header/{id}/{Name}/{hungrig}\""
                       <> withFormattedCaptures " " pathParts

Failures:

  test/Servant/PY/InternalSpec.hs:131:7: 
  1) Servant.PY.Internal.Servant.PY.Internal.Internal, functions that operate on Req objects, should build urls properly with / separator
       expected: "\"urlForRequesting:9000/login-with-path-var-and-header/{id}/{Name}/{hungrig}\".format(\n id=parse.quote(str(id)),\n Name=parse.quote(str(Name)),\n hungrig=parse.quote(str(hungrig)))"
        but got: "\"urlForRequesting:9000/login-with-path-var-and-header/{id}/{Name}/{hungrig}\".format(\n id=parse.quote(str(id)),\n Name=parse.quote(str(Name)),\n hungrig=parse.quote(str(hungrig)))\""