[BUG] Invalid function names based on strings containing # and digits

[spacether]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
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Description

Invalid function names are generated from enum string values resembling "#367B9C".

openapi-generator version

latest via docker CLI

OpenAPI declaration file content or url

Minimal reproduction: gist, validated with vacuum

Generation Details

docker run --rm -v ${PWD}:/local openapitools/openapi-generator-cli:latest generate --global-property skipFormModel=false -i /local/color-names.json -g python -o /local/openapi-client

Steps to reproduce

After generating, install generated code and run pytest.

Output:

openapi-client\test\test_paths\test_sample_json\test_post.py:15: in <module>
    from openapi_client.paths.sample_json import post  # noqa: E501
E     File "C:\Users\Work\Code\openapi-generator-repros\openapi-client\openapi_client\paths\sample_json\post.py", line 90
E       def 67B9C(cls):
E            ^
E   SyntaxError: invalid decimal literal

Original bug from: OpenAPITools/openapi-generator#13942