title: Code won't go into the except clause for error handling
body: <p>I am new to python and am trying to make some code work. In the code I force an error and hope to activate the error handler. </p>
  
  <p>I have tried to google this problem, but not been able to find a solution...</p>
  
  <pre class="lang-py prettyprint-override"><code>#Main code
  from Calculations import Errormessages as em
  x = 'a'
  try:
      y = 2/x
      print("y is:", y)
  
  except em.error_str_input:
      print("This works (1)")
  
  except error_0_input:
      print("This works (2)")
  
  #From the Errormessages-file I import the following code:
  class error(Exception):
      print("Wrong instruction given, please try again ...")
      pass
  class error_str_input(error):
      print("... input numbers (not strings)!")
      pass
  class error_0_input(error):
      print("... cannot divide by zero!")
      pass
  </code></pre>
  
  <p>I had expected:</p>
  
  <pre><code>Wrong instruction given, please try again ...
  ... input numbers (not strings)!
  This works (1)
  </code></pre>
  
  <p>But resulted in the following error message:</p>
  
  <pre><code>File "//.../file.py", line 10, in &lt;module&gt;
      y = 2/x
  TypeError: unsupported operand type(s) for /: 'int' and 'str'
  </code></pre>