title: Unsupported operand type for NoneType and str
body: <p>I get a message that states:</p>
  
  <pre><code>Traceback (most recent call last):
   File "/var/www/fosa/error_supressor.py", line 46, in &lt;module&gt;
     sys.stderr.write(latest + '\n')
  TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
  </code></pre>
  
  <p>I have been trying to solve this problem for days now but honestly I'm a rocky programmer.
  So let's line up the problem and see if there is a patient person that can spare some time solving a humble stranger's problem :-)</p>
  
  <p>Besides that when I check my error log I find this error message, which I suspect is related:</p>
  
  <pre><code>File "/var/www/fosa/app/controllers/client/client.py", line 601, in detail
      if not course.bookable or not course.school.partner.active: # both objects are boolean 
  AttributeError: 'NoneType' object has no attribute 'bookable'
  </code></pre>