code: def travis_build_package():
      
      travis_tag = os.environ.get("TRAVIS_TAG")
      if not travis_tag:
          print("TRAVIS_TAG environment variable is not present")
          return "TRAVIS_TAG environment variable is not present"
  
      try:
          version = Version(travis_tag)
      except InvalidVersion:
          failure = "Version must be a valid PEP440 version (version is: {})".format(version)
          print(failure)
          return failure
  
      abs_dist_path = Path(os.environ["TRAVIS_BUILD_DIR"], "dist")
      [create_package(package, text_type(abs_dist_path)) for package in package_list]
  
      print("Produced:\n{}".format(list(abs_dist_path.glob("*"))))
  
      pattern = "*{}*".format(version)
      packages = list(abs_dist_path.glob(pattern))
      if not packages:
          return "Package version does not match tag {}, abort".format(version)
      pypi_server = os.environ.get("PYPI_SERVER", "default PyPI server")
      print("Package created as expected and will be pushed to {}".format(pypi_server))
docs: Assumed called on Travis, to prepare a package to be deployed
      This method prints on stdout for Travis.
      Return is obj to pass to sys.exit() directly