title: Pip says 'pip install --upgrade pip' but 'pip: command not found'
body: <p><strong>My environment:</strong></p>
  <ul>
  <li>macOS 10.14.6</li>
  <li>Python 2.7.10</li>
  <li>Python 3.6.5</li>
  <li>pip  10.0.1</li>
  </ul>
  <p><strong>My situation:</strong></p>
  <p>I am trying to use OpenCV.
  When I write this command</p>
  <pre><code>$ pip3 install virtualenv virtualenvwrapper
  </code></pre>
  <p>and then pip say this.</p>
  <blockquote>
  <p>pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.</p>
  <p>You are using pip version 10.0.1, however version 19.3.1 is available.</p>
  <p>You should consider upgrading via the 'pip install --upgrade pip' command.</p>
  </blockquote>
  <p>So I try this</p>
  <pre><code>pip install --upgrade pip 
  </code></pre>
  <p>and then</p>
  <blockquote>
  <p>-bash: pip: command not found</p>
  </blockquote>
  <p>I also did this</p>
  <pre><code>pip3 install --upgrade pip
  </code></pre>
  <p>and then</p>
  <blockquote>
  <p>pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.</p>
  <p>Could not fetch URL <a href="https://pypi.org/simple/pip/" rel="nofollow noreferrer">https://pypi.org/simple/pip/</a>: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError(&quot;Can't connect to HTTPS URL because the SSL module is not available.&quot;,)) - skipping</p>
  <p>Requirement already up-to-date: pip in /usr/local/lib/python3.6/site-packages (10.0.1)</p>
  </blockquote>
  <p><strong>What I tried</strong></p>
  <p>1: Uninstall pip</p>
  <pre><code>sudo pip uninstall pip
  </code></pre>
  <p>2: Uninstall Homebrew</p>
  <pre><code>ruby -e &quot;$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)&quot;
  </code></pre>
  <p>3: Reinstall Homebrew and the packages</p>
  <p>4: Downgrade Python 3.7 to Python 3.6 to install OpenCV.</p>