[Ruby] generated client contains syntax errors when enum includes single-quote

Description

When enum contains item single-quote, the generated Ruby client code contains syntax errors.

Swagger-codegen version

$ java -jar modules/swagger-codegen-cli/target/swagger-codegen-cli.jar version
2.4.2-SNAPSHOT

$ git log --oneline -n 1
c4c5c062c Merge pull request #9080 from swagger-api/update-parser-v1

Swagger declaration file content or url

See: https://gist.github.com/autopp/f1c6f438a050148cefe3d6cbbc0f8a81

The point to notice in this example is that ' is included in two enums.

Command line used for generation

java -jar modules/swagger-codegen-cli/target/swagger-codegen-cli.jar generate -i 'https://gist.githubusercontent.com/autopp/f1c6f438a050148cefe3d6cbbc0f8a81/raw/4c8cce86d5b258ec08490b2aa28e59400c854150/swagger.yml' -l ruby -o /tmp/gem

Steps to reproduce

1. Run the above command to generate client code for Ruby.
2. Run ruby -c /tmp/gem/lib/swagger_client/api/default_api.rb and ruby -c /tmp/gem/lib/swagger_client/models/x.rb to check syntax of generated codes.
3. Get errors in lib/swagger_client/models/x.rb and lib/swagger_client/api_client.rb:

/tmp/gem/lib/swagger_client/api/default_api.rb:37: syntax error, unexpected tIDENTIFIER, expecting ']'
...] && !['''].include?(opts[:'foo'])
...                            ^~~
/tmp/gem/lib/swagger_client/api/default_api.rb:38: syntax error, unexpected tIDENTIFIER, expecting keyword_end
...   fail ArgumentError, 'invalid value for "foo", must be one...
...                        ^~~~~~~
/tmp/gem/lib/swagger_client/api/default_api.rb:38: syntax error, unexpected ',', expecting &. or ::or '[' or '.'
...rror, 'invalid value for "foo", must be one of''
...                              ^
/tmp/gem/lib/swagger_client/api/default_api.rb:65: Invalid return in class/module body
      return data, status_code, headers
      ^~~~~~
/tmp/gem/lib/swagger_client/api/default_api.rb:109: syntax error, unexpected keyword_end, expectingend-of-input

/tmp/gem/lib/swagger_client/models/x.rb:86: syntax error, unexpected tCONSTANT, expecting ']'
...mAttributeValidator.new('String', ["'"])
...                         ^~~~~~
/tmp/gem/lib/swagger_client/models/x.rb:88: syntax error, unexpected tIDENTIFIER, expecting keyword_end
...entError, 'invalid value for "y", must be one of #{validator...
...                              ^
/tmp/gem/lib/swagger_client/models/x.rb:125: syntax error, unexpected keyword_elsif, expecting keyword_end
        elsif !attributes[self.class.attri...
        ^~~~~
/tmp/gem/lib/swagger_client/models/x.rb:131: syntax error, unexpected keyword_end, expecting end-of-input
    end
    ^~~

Related issues/PRs

#9091 is similar probrem.

Suggest a fix/enhancement

Current escapeText of RubyClientCodegen does not seem to be for single quote strings.

Start by locating RubyClientCodegen and its current escapeText implementation, then reproduce the issue with the linked Swagger declaration and the documented generate command. Run ruby -c on the generated default_api.rb, x.rb, and api_client.rb files; done means enum values containing a single quote no longer produce Ruby syntax errors.