Handle CGI SSL detection via HTTPS environment better.

Some servers send on/off, 0/1, yes/no, and may be upper or lower case.
This fix will handle all of those permutations. It was inspired by the
detection done in in some other wsgi python web applications I looked at.

mercurial/hgweb/wsgicgi.py

@@ -1,73 +1,73
 # hgweb/wsgicgi.py - CGI->WSGI translator
 #
 # Copyright 2006 Eric Hopper <[e-mail]>
 #
 # This software may be used and distributed according to the terms
 # of the GNU General Public License, incorporated herein by reference.
 #
 # This was originally copied from the public domain code at
 # http://www.python.org/dev/peps/pep-0333/#the-server-gateway-side
 
 import os, sys
 from mercurial import util
 
 def launch(application):
     util.set_binary(sys.stdin)
     util.set_binary(sys.stdout)
 
     environ = dict(os.environ.items())
     environ['wsgi.input'] = sys.stdin
     environ['wsgi.errors'] = sys.stderr
     environ['wsgi.version'] = (1, 0)
     environ['wsgi.multithread'] = False
     environ['wsgi.multiprocess'] = True
     environ['wsgi.run_once'] = True
 
-    if environ.get('HTTPS','off') in ('on','1'):
+    if environ.get('HTTPS','off').lower() in ('on','1','yes'):
         environ['wsgi.url_scheme'] = 'https'
     else:
         environ['wsgi.url_scheme'] = 'http'
 
     headers_set = []
     headers_sent = []
     out = sys.stdout
 
     def write(data):
         if not headers_set:
             raise AssertionError("write() before start_response()")
 
         elif not headers_sent:
             # Before the first output, send the stored headers
             status, response_headers = headers_sent[:] = headers_set
             out.write('Status: %s\r\n' % status)
             for header in response_headers:
                 out.write('%s: %s\r\n' % header)
             out.write('\r\n')
 
         out.write(data)
         out.flush()
 
     def start_response(status, response_headers, exc_info=None):
         if exc_info:
             try:
                 if headers_sent:
                     # Re-raise original exception if headers sent
                     raise exc_info[0], exc_info[1], exc_info[2]
             finally:
                 exc_info = None     # avoid dangling circular ref
         elif headers_set:
             raise AssertionError("Headers already set!")
 
         headers_set[:] = [status, response_headers]
         return write
 
     result = application(environ, start_response)
     try:
         for data in result:
             if data:    # don't send headers until body appears
                 write(data)
         if not headers_sent:
             write('')   # send headers now if body was empty
     finally:
         if hasattr(result,'close'):
             result.close()