4- 5 Pass in an app, the PATH_INFO, the request method
      (GET/POST/etc), the body of the request (typically POST vars),
      and any overrides for the WSGI environ.

 6- 7  Create the full WSGI environ:
27-31  Encode the body if it's a dictionary
32-33  Set wsgi.input to the body, CONTENT_LENGTH to its length
   34  Capture wsgi.errors
35-59  Set other standard WSGI variables
40-45  Split QUERY_STRING from PATH_INFO
46-49  Set other standard CGI variables
   50  Set host to localhost

   13  Run the application
10-11  Capture status and headers
16-17  Capture response body
18-19  Call app_iter.close() if possible
21-23  Put status, headers, body into a response object:
70-82  The response object has a __str__ that shows a representation
         suitable for doctest
55-60  And attributes for everything else