title: Pip install on Mac OS gets error: command '/usr/bin/clang' failed with exit code 1
body: <p>I want to install google-cloud-pubsub via pip installation on Mac OS but I get an error: <code>distutils.errors.CompileError: command '/usr/bin/clang' failed with exit code 1</code>. The command I run: <code>pip install google-cloud-pubsub==2.1.0</code>.</p>
  <p>Here the complete <a href="https://storage.googleapis.com/fausto-labs/trace.txt" rel="noreferrer">error message</a>.</p>
  <p>Any suggestion? Thank you!</p>
  <p>More info:</p>
  <pre><code>$ python -V
  Python 3.9.0
  
  $ pip -V
  pip 20.2.4 from /.../lib/python3.9/site-packages/pip (python 3.9)
  
  $ sw_vers
  ProductName:    macOS
  ProductVersion: 11.0.1
  BuildVersion:   20B29
  </code></pre>
  <p>I've seen other similar cases but them don't solve my issue. I tried:</p>
  <ul>
  <li><a href="https://stackoverflow.com/questions/53654896/pip-install-error-in-mac-oserror-command-usr-bin-clang-failed-with-exit-sta">Pip install error in Mac OS(error: command '/usr/bin/clang' failed with exit status 1)</a></li>
  <li><a href="https://github.com/velocyto-team/velocyto.py/issues/191" rel="noreferrer">Mac OS Mojave installation error - error: command 'clang' failed with exit status 1</a></li>
  </ul>