title: Python: "ModuleNotFoundError", but module is installed?
body: <p>I realize this seems like a generic question, but all answers pointed to having two simultanious <code>python</code> installations - I already uninstalled the other one.</p>
  
  <p>Currently I run my code from <em>PyCharm 2017.1.5</em> (windows 10) with Python interpreter set as <code>Python 3.6.1 (C:\Anaconda3\python.exe)</code>, i.e. I installed <em>Anaconda3</em>, which includes the <code>matplotlib</code>, and run from <em>PyCharm</em> using the <em>Ananconda3</em>-interpreter.</p>
  
  <p>I've checked in <em>Anaconda Navigator</em> that <code>matplotlib 2.0.2</code> is installed in the environment.</p>
  
  <p>A minimal (non-working) example:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  
  plt.plot(range(10))
  plt.show()
  </code></pre>
  
  <p>Returns the following error:</p>
  
  <pre><code>C:\Anaconda3\python.exe C:/Users/John/Documents/CPU/master/untitled/main11.py
  Traceback (most recent call last):
    File "C:/Users/John/Documents/CPU/master/untitled/main11.py", line 1, in &lt;module&gt;
      import matplotlib.pyplot as plt
    File "C:\Anaconda3\lib\site-packages\matplotlib\pyplot.py", line 29, in &lt;module&gt;
      import matplotlib.colorbar
    File "C:\Anaconda3\lib\site-packages\matplotlib\colorbar.py", line 34, in &lt;module&gt;
      import matplotlib.collections as collections
    File "C:\Anaconda3\lib\site-packages\matplotlib\collections.py", line 37, in &lt;module&gt;
      import matplotlib.lines as mlines
    File "C:\Anaconda3\lib\site-packages\matplotlib\lines.py", line 28, in &lt;module&gt;
      from matplotlib.markers import MarkerStyle
  ModuleNotFoundError: No module named 'matplotlib.markers'
  
  Process finished with exit code 1
  </code></pre>
  
  <p>This ran fine 2 weeks ago, but not now. To my knowledge, I didn't change or update anything. The module loads correctly, but it seems to be a change in the module content? If so: How did that happen and how can I fix it?</p>