[BUG] version 4.0.0.beta3 fails to start the nodejs-server generated code

[javadch]

• Install NVM, npm 6.9.0, and openapi-generator 4.0.0.beta3
• downlaod petstore.yaml and validate uding the validate command
• generate a nodejs-server using npx openapi-generator generate -i temp/node/petstore.yaml -g nodejs-server -o temp/node/out
• cd temp/node/out
• npm start
  This command fails reporting:
  /home/javadch/temp/node/out/node_modules/swagger-tools/lib/helpers.js:169 throw new Error('Unsupported Swagger version: ' + version); ^ Error: Unsupported Swagger version: undefined

OpenAPITools uses apigee, which says it supports swagger 1 and 2 only, while OpenAPITools support 3 too.

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