[BUG][Python3.7][openapi-generator-cli] ImportError: cannot import name 'GenericMeta' from 'typing'

Description

When running python client package in python 3.7 runtime, it raised error ImportError: cannot import name 'GenericMeta' from 'typing'

• typing.GenericMeta is not available in Python 3.7
• add ImportError exception

openapi-generator version

• openapitools/openapi-generator-cli:v4.3.1

Steps to reproduce

Traceback (most recent call last):
  File "/***/python37_lab/test.py", line 3, in <module>
    import nomad_envoy_cli
  File "/***/.virtualenvs/py37/lib/python3.7/site-packages/nomad_envoy_cli/__init__.py", line 21, in <module>
    from nomad_envoy_cli.api.customs_api import CustomsApi
  File "/***/.virtualenvs/py37/lib/python3.7/site-packages/nomad_envoy_cli/api/__init__.py", line 6, in <module>
    from nomad_envoy_cli.api.customs_api import CustomsApi
  File "/***/.virtualenvs/py37/lib/python3.7/site-packages/nomad_envoy_cli/api/customs_api.py", line 21, in <module>
    from nomad_envoy_cli.api_client import ApiClient
  File "/***/.virtualenvs/py37/lib/python3.7/site-packages/nomad_envoy_cli/api_client.py", line 681, in <module>
    from .swagger_validator import SwaggerValidator
  File "/***/.virtualenvs/py37/lib/python3.7/site-packages/nomad_envoy_cli/swagger_validator.py", line 4, in <module>
    from typing import List, AnyStr, Any, Type, GenericMeta, Dict
ImportError: cannot import name 'GenericMeta' from 'typing' (/usr/local/Cellar/python/3.7.5/Frameworks/Python.framework/Versions/3.7/lib/python3.7/typing.py)

Related issues/PRs

https://github.com/OpenAPITools/openapi-generator/issues/2022

Suggest a fix

error version:

import importlib
import json
from datetime import date, datetime
from typing import List, AnyStr, Any, Type, GenericMeta, Dict

class SwaggerValidator(object):

fixed:

import importlib
import json
from datetime import date, datetime
from typing import List, AnyStr, Any, Type, GenericMeta, Dict
try:
    from typing import GenericMeta  # python 3.6
except ImportError:
    # in 3.7, genericmeta doesn't exist but we don't need it
    class GenericMeta(type): pass

class SwaggerValidator(object):

Start with the generated Python client's swagger_validator.py, identified in the traceback, and reproduce the import under Python 3.7. Check the typing import and the reported compatibility behavior, then verify that importing the client succeeds on Python 3.7 and that the relevant generated-client tests pass.