old_contents: # Copyright 2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License"). You
  # may not use this file except in compliance with the License. A copy of
  # the License is located at
  #
  # http://aws.amazon.com/apache2.0/
  #
  # or in the "license" file accompanying this file. This file is
  # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
  # ANY KIND, either express or implied. See the License for the specific
  # language governing permissions and limitations under the License.
  import os
  import uuid
  
  _ORIGINAL = os.environ.copy()
  # These are environment variables that allow users to control
  # the location of config files used by botocore.
  _CONFIG_FILE_ENV_VARS = [
      'AWS_CONFIG_FILE',
      'AWS_SHARED_CREDENTIALS_FILE',
      'BOTO_CONFIG',
  ]
  _CREDENTIAL_ENV_VARS = [
      'AWS_ACCESS_KEY_ID',
      'AWS_SECRET_ACCESS_KEY',
      'AWS_SESSION_TOKEN',
  ]
  
  
  def setup_package():
      random_file = str(uuid.uuid4())
      for varname in _CONFIG_FILE_ENV_VARS:
          os.environ[varname] = random_file
      for credvar in _CREDENTIAL_ENV_VARS:
          os.environ.pop(credvar, None)
  
  
  def teardown_package():
      os.environ = _ORIGINAL
  
new_contents: # Copyright 2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License"). You
  # may not use this file except in compliance with the License. A copy of
  # the License is located at
  #
  # http://aws.amazon.com/apache2.0/
  #
  # or in the "license" file accompanying this file. This file is
  # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
  # ANY KIND, either express or implied. See the License for the specific
  # language governing permissions and limitations under the License.
  import os
  import uuid
  
  _ORIGINAL = os.environ.copy()
  # These are environment variables that allow users to control
  # the location of config files used by botocore.
  _CONFIG_FILE_ENV_VARS = [
      'AWS_CONFIG_FILE',
      'AWS_SHARED_CREDENTIALS_FILE',
      'BOTO_CONFIG',
  ]
  _CREDENTIAL_ENV_VARS = [
      'AWS_ACCESS_KEY_ID',
      'AWS_SECRET_ACCESS_KEY',
      'AWS_SESSION_TOKEN',
  ]
  
  
  def setup_package():
      # We're using a random uuid to ensure we're pointing
      # AWS_CONFIG_FILE and other env vars at a filename that
      # does not exist.
      random_file = str(uuid.uuid4())
      for varname in _CONFIG_FILE_ENV_VARS:
          # The reason we're doing this is to ensure we don't automatically pick
          # up any credentials a developer might have configured on their local
          # machine.  Travis will not have any credentials available, so without
          # this fixture setup, it's possible to have all the tests pass on your
          # local machine (if you have credentials configured) but still fail on
          # travis.
          os.environ[varname] = random_file
      for credvar in _CREDENTIAL_ENV_VARS:
          os.environ.pop(credvar, None)
  
  
  def teardown_package():
      os.environ = _ORIGINAL
  
subject: Add a comment about why the package fixture is needed