title: Getting an error with pip3 : ModuleNotFoundError: No module named 'pip._vendor.packaging.__about__'
body: <p>Whenever I try using <code>pip3</code> or anything that contains <code>pip3</code>, I get the following error:</p>
  <pre><code>ModuleNotFoundError: No module named 'pip._vendor.packaging.__about__' pops up.
  </code></pre>
  <p>I used it to install <code>opencv</code> and used <code>opencv</code> for multiple projects yesterday. I have no idea why the error popped up today.</p>
  <p>Here is my code:</p>
  <pre><code>kaushiksankar@Kaushiks-MacBook-Pro ~ % pip3 install opencv-python
  Traceback (most recent call last):
    File &quot;/Library/Frameworks/Python.framework/Versions/3.9/bin/pip3&quot;, line 5, in &lt;module&gt;
      from pip._internal.cli.main import main
    File &quot;/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pip/_internal/cli/main.py&quot;, line 10, in &lt;module&gt;
      from pip._internal.cli.autocompletion import autocomplete
    File &quot;/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pip/_internal/cli/autocompletion.py&quot;, line 9, in &lt;module&gt;
      from pip._internal.cli.main_parser import create_main_parser
    File &quot;/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pip/_internal/cli/main_parser.py&quot;, line 7, in &lt;module&gt;
      from pip._internal.cli import cmdoptions
    File &quot;/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pip/_internal/cli/cmdoptions.py&quot;, line 23, in &lt;module&gt;
      from pip._internal.cli.progress_bars import BAR_TYPES
    File &quot;/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pip/_internal/cli/progress_bars.py&quot;, line 12, in &lt;module&gt;
      from pip._internal.utils.logging import get_indentation
    File &quot;/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pip/_internal/utils/logging.py&quot;, line 17, in &lt;module&gt;
      from pip._internal.utils.deprecation import DEPRECATION_MSG_PREFIX
    File &quot;/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pip/_internal/utils/deprecation.py&quot;, line 13, in &lt;module&gt;
      from pip._vendor.packaging.version import parse
    File &quot;/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pip/_vendor/packaging/__init__.py&quot;, line 6, in &lt;module&gt;
      from .__about__ import (
  ModuleNotFoundError: No module named 'pip._vendor.packaging.__about__'
  </code></pre>
  <p>I am using MacOS.</p>
  <p>I cannot find the version of <code>pip</code> by any method.
  <code>pip</code> command cannot be used, hence used <code>pip3</code>.</p>