title: pip show does not show the package but I can import it
body: <p>I'm using venv, created by <code>python3 -m venv .venv</code>. It's runnig python 3.6.9.</p>
  <p>When I run <code>pip show tensorflow</code> in venv, it returns <code>WARNING: Package(s) not found: tensorflow</code>. However, in a python interpreter, I can import it (still, in venv):</p>
  <pre class="lang-py prettyprint-override"><code>import tensorflow as tf
  print(tf.__version__)  # 1.15.0
  </code></pre>
  <p><code>which python</code> and <code>which pip</code> returns:</p>
  <pre class="lang-sh prettyprint-override"><code>.../.venv/bin/python
  .../.venv/bin/pip
  </code></pre>
  <p>Additional information: I tried to dockerize this project. When I try to run it, it throw error: <code>ModuleNotFoundError: No module named 'tensorflow'</code>, which I think makes sense, because I don't have it in my <code>requirements.txt</code>. But without docker, I can import <code>tensorflow</code> both in interpreter and in a module.</p>
  <p>I don't know what or which part is wrong here; docker or pip?</p>