Fix single quote escaping for python code generator (and its test)

[curdbecker]

Currently, the implementation of the code generator for Python can generate invalid Python code if single quotes are used within an OpenAPI specification, e.g. for default values. Please see also this issue that I have created.

This stems from invalid single quote escaping within the generator. It's kind of hard to spot, but in Java the strings "'" and "'" are identical, so the implementation and its test were broken identically.

This seems to have happened already quite a few years ago during refactoring, since the test seems might have been created as a result of this issue.

The minimal example from there is still valid:

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: Single quote example
  version: 1.0.0
paths:
  /singleQuoteExample:
    post:
      summary: Test single quote in default and example values.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                singleQuoteInDefault1:
                  type: string
                  default: Text containing 'single' quote
                singleQuoteInDefault2:
                  type: string
                  default: "8'998'999'998'000'000"
                singleQuoteInExample1:
                  type: string
                  example: "Text containing 'single' quote"
                singleQuoteInExample2:
                  type: string
                  example: 8'998'999'998'000'000
      responses:
        '201':
          description: OK

Command line used for generation

docker run --rm -v $(pwd)/bla:/bla -v $(pwd):/local openapitools/openapi-generator-cli:latest generate -i /local/bla.yaml -g python -o /bla

Steps to reproduce

Run the above command.

Expected output

bla/openapi_client/models/single_quote_example_post_request.py

class SingleQuoteExamplePostRequest(BaseModel):
    """
    SingleQuoteExamplePostRequest
    """ # noqa: E501
    single_quote_in_default1: Optional[StrictStr] = Field(default='Text containing \'single\' quote', alias="singleQuoteInDefault1")
    single_quote_in_default2: Optional[StrictStr] = Field(default='8\'998\'999\'998\'000\'000', alias="singleQuoteInDefault2")
    single_quote_in_example1: Optional[StrictStr] = Field(default=None, alias="singleQuoteInExample1")
    single_quote_in_example2: Optional[StrictStr] = Field(default=None, alias="singleQuoteInExample2")
    __properties: ClassVar[List[str]] = ["singleQuoteInDefault1", "singleQuoteInDefault2", "singleQuoteInExample1", "singleQuoteInExample2"]

Actual output

bla/openapi_client/models/single_quote_example_post_request.py

class SingleQuoteExamplePostRequest(BaseModel):
    """
    SingleQuoteExamplePostRequest
    """ # noqa: E501
    single_quote_in_default1: Optional[StrictStr] = Field(default='Text containing 'single' quote', alias="singleQuoteInDefault1")
    single_quote_in_default2: Optional[StrictStr] = Field(default='8'998'999'998'000'000', alias="singleQuoteInDefault2")
    single_quote_in_example1: Optional[StrictStr] = Field(default=None, alias="singleQuoteInExample1")
    single_quote_in_example2: Optional[StrictStr] = Field(default=None, alias="singleQuoteInExample2")
    __properties: ClassVar[List[str]] = ["singleQuoteInDefault1", "singleQuoteInDefault2", "singleQuoteInExample1", "singleQuoteInExample2"]

@cbornet @tomplus @krjakbrjak @fa0311 @multani

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[wing328]

thanks for the PR, which has been merged