title: AttributeError: module 'pystan' has no attribute 'StanModel'
body: <p>After running the following line (already exist the package):</p>
  
  <pre><code>pip install -vvv pystan
  
  Requirement already satisfied: pystan in /Users/cmougan/anaconda3/lib/python3.6/site-packages (2.17.1.0)
  Requirement already satisfied: Cython!=0.25.1,&gt;=0.22 in /Users/cmougan/anaconda3/lib/python3.6/site-packages (from pystan) (0.28.2)
  Requirement already satisfied: numpy&gt;=1.7 in /Users/cmougan/anaconda3/lib/python3.6/site-packages (from pystan) (1.16.2)
  Carloss-MacBook-Pro:Desktop cmougan$ pip install -vvv pystan
  Non-user install because site-packages writeable
  Created temporary directory: /private/var/folders/j6/tcx3t7vj4fs8rsb97cwg06nc0000gn/T/pip-ephem-wheel-cache-0p2f3viv
  Created temporary directory: /private/var/folders/j6/tcx3t7vj4fs8rsb97cwg06nc0000gn/T/pip-req-tracker-lg301zxr
  Initialized build tracking at /private/var/folders/j6/tcx3t7vj4fs8rsb97cwg06nc0000gn/T/pip-req-tracker-lg301zxr
  Created build tracker: /private/var/folders/j6/tcx3t7vj4fs8rsb97cwg06nc0000gn/T/pip-req-tracker-lg301zxr
  Entered build tracker: /private/var/folders/j6/tcx3t7vj4fs8rsb97cwg06nc0000gn/T/pip-req-tracker-lg301zxr
  Created temporary directory: /private/var/folders/j6/tcx3t7vj4fs8rsb97cwg06nc0000gn/T/pip-install-8ffjd5t4
  Requirement already satisfied: pystan in /Users/cmougan/anaconda3/lib/python3.6/site-packages (2.17.1.0)
  Requirement already satisfied: Cython!=0.25.1,&gt;=0.22 in /Users/cmougan/anaconda3/lib/python3.6/site-packages (from pystan) (0.28.2)
  Requirement already satisfied: numpy&gt;=1.7 in /Users/cmougan/anaconda3/lib/python3.6/site-packages (from pystan) (1.16.2)
  Removed build tracker: '/private/var/folders/j6/tcx3t7vj4fs8rsb97cwg06nc0000gn/T/pip-req-tracker-lg301zxr'
  
  
  </code></pre>
  
  <p>I perform the following:</p>
  
  <pre class="lang-py prettyprint-override"><code>import pystan
  model_code = 'parameters {real y;} model {y ~ normal(0,1);}'
  model = pystan.StanModel(model_code=model_code)  # this will take a minute
  y = model.sampling(n_jobs=1).extract()['y']
  y.mean()  # should be close to 0
  </code></pre>
  
  <p>And I get the following error:</p>
  
  <pre class="lang-py prettyprint-override"><code>---------------------------------------------------------------------------
  AttributeError                            Traceback (most recent call last)
  &lt;ipython-input-40-d7f147a8ee3e&gt; in &lt;module&gt;
        1 import pystan
        2 model_code = 'parameters {real y;} model {y ~ normal(0,1);}'
  ----&gt; 3 model = pystan.StanModel(model_code=model_code)  # this will take a minute
        4 y = model.sampling(n_jobs=1).extract()['y']
        5 y.mean()  # should be close to 0
  
  AttributeError: module 'pystan' has no attribute 'StanModel'
  </code></pre>
  
  <p>I am using python 3.6 and pip. I am using the flag -vvv for more verbose to help in the debugging of the error.</p>