title: AttributeError: 'AuthorizedSession' object has no attribute 'configure_mtls_channel'
body: <p>I was orchestrating two dataflow job with cloud composer and it was working fine for month. Suddenly the two jobs stopped working with the following error message:</p>
  <blockquote>
  <p>in download_blob File
  &quot;/usr/local/lib/python3.6/site-packages/google/cloud/storage/client.py&quot;,
  line 399, in get_bucket retry=retry, File
  &quot;/usr/local/lib/python3.6/site-packages/google/cloud/storage/bucket.py&quot;,
  line 1002, in reload retry=retry, File
  &quot;/usr/local/lib/python3.6/site-packages/google/cloud/storage/_helpers.py&quot;,
  line 225, in reload retry=retry, File
  &quot;/usr/local/lib/python3.6/site-packages/google/cloud/storage/_http.py&quot;,
  line 63, in api_request return call() File
  &quot;/usr/local/lib/python3.6/site-packages/google/api_core/retry.py&quot;,
  line 286, in retry_wrapped_func on_error=on_error, File
  &quot;/usr/local/lib/python3.6/site-packages/google/api_core/retry.py&quot;,
  line 184, in retry_target return target() File
  &quot;/usr/local/lib/python3.6/site-packages/google/cloud/_http.py&quot;, line
  479, in api_request timeout=timeout, File
  &quot;/usr/local/lib/python3.6/site-packages/google/cloud/_http.py&quot;, line
  337, in _make_request method, url, headers, data, target_object,
  timeout=timeout File
  &quot;/usr/local/lib/python3.6/site-packages/google/cloud/_http.py&quot;, line
  374, in _do_request return self.http.request( File
  &quot;/usr/local/lib/python3.6/site-packages/google/cloud/_http.py&quot;, line
  157, in http return self._client._http File
  &quot;/usr/local/lib/python3.6/site-packages/google/cloud/client.py&quot;, line
  187, in _http
  self._http_internal.configure_mtls_channel(self._client_cert_source)
  AttributeError: 'AuthorizedSession' object has no attribute
  'configure_mtls_channel'</p>
  </blockquote>
  <p>In the jobs I download a file from google cloud storage with the storage client. I assumed it was because of some dependencies issues. In the composer environment I installed google-cloud-storage without specifying a version. I tried specifying different versions of the package but nothing seems to work.</p>
  <p>Thanks!</p>