title: Keras is installed in Anaconda virtual environment but can't be imported
body: <p>I have <code>keras</code> installed into my Anaconda virtual environment but I can't import the module:</p>
  
  <pre><code>$ conda list | grep keras
  keras                     2.2.4                    py37_1    conda-forge
  keras-applications        1.0.8                      py_0  
  keras-preprocessing       1.1.0                      py_1  
  keras-retinanet           0.5.0                    pypi_0    pypi
  
  $ python
  Python 3.7.3 | packaged by conda-forge | (default, Mar 27 2019, 23:01:00) 
  [GCC 7.3.0] :: Anaconda, Inc. on linux
  Type "help", "copyright", "credits" or "license" for more information.
  &gt;&gt;&gt; import keras
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  ModuleNotFoundError: No module named 'keras'
  </code></pre>
  
  <p>What might be amiss?</p>