Python 3 preparation: HTTP headers handling in roundup_server.py.

HTTP headers are handled differently in Python 3 (where they use
email.message.Message) compared to Python 2 (where they use
mimetools.Message).  In some places the code needs to check which
version of the interface is available.  For the common case of getting
a single header, ".get" is available in both versions, and is an alias
of ".getheader" in Python 2.  (Note that the Python 3 semantics of
".get" are slightly different from those in Python 2 if there is more
than one of a given header - it returns an arbitrary one, when in
Python 2 it's specified to return the last one.  Hopefully the places
using this interface rather than explicitly allowing for multiple
headers with the same name are OK with that and it shouldn't actually
occur with well-behaved clients.)

Author: jsm28

roundup/scripts/roundup_server.py

@@ -375,17 +375,28 @@ def inner_run_cgi(self):
         env['PATH_INFO'] = urllib_.unquote(rest)
         if query:
             env['QUERY_STRING'] = query
-        if self.headers.typeheader is None:
+        if hasattr(self.headers, 'get_content_type'):
+            # Python 3.  We need the raw header contents.
+            env['CONTENT_TYPE'] = self.headers.get('content-type')
+        elif self.headers.typeheader is None:
+            # Python 2.
             env['CONTENT_TYPE'] = self.headers.type
         else:
+            # Python 2.
             env['CONTENT_TYPE'] = self.headers.typeheader
-        length = self.headers.getheader('content-length')
+        length = self.headers.get('content-length')
         if length:
             env['CONTENT_LENGTH'] = length
-        co = list(filter(None, self.headers.getheaders('cookie')))
+        if hasattr(self.headers, 'get_all'):
+            # Python 3.
+            ch = self.headers.get_all('cookie', [])
+        else:
+            # Python 2.
+            ch = self.headers.getheaders('cookie')
+        co = list(filter(None, ch))
         if co:
             env['HTTP_COOKIE'] = ', '.join(co)
-        env['HTTP_AUTHORIZATION'] = self.headers.getheader('authorization')
+        env['HTTP_AUTHORIZATION'] = self.headers.get('authorization')
         env['SCRIPT_NAME'] = ''
         env['SERVER_NAME'] = self.server.server_name
         env['SERVER_PORT'] = str(self.server.server_port)
@@ -395,13 +406,13 @@ def inner_run_cgi(self):
             env['HTTP_HOST'] = ''
         # https://tools.ietf.org/html/draft-ietf-appsawg-http-forwarded-10
         # headers.
-        xfh = self.headers.getheader('X-Forwarded-Host', None)
+        xfh = self.headers.get('X-Forwarded-Host', None)
         if xfh:
             # If behind a proxy, this is the hostname supplied
             # via the Host header to the proxy. Used by core code.
             # Controlled by the CSRF settings.
             env['HTTP_X-FORWARDED-HOST'] = xfh
-        xff = self.headers.getheader('X-Forwarded-For', None)
+        xff = self.headers.get('X-Forwarded-For', None)
         if xff:
             # xff is a list of ip addresses for original client/proxies:
             # X-Forwarded-For: clientIP, proxy1IP, proxy2IP
@@ -411,7 +422,7 @@ def inner_run_cgi(self):
             # E.g. you may wish to disable recaptcha validation extension
             # if the ip of the client matches 172.16.0.0.
             env['HTTP_X-FORWARDED-FOR'] = xff
-        xfp = self.headers.getheader('X-Forwarded-Proto', None)
+        xfp = self.headers.get('X-Forwarded-Proto', None)
         if xfp:
             # xfp is the protocol (http/https) seen by proxies in the
             # path of the request. I am not sure if there is only
@@ -437,7 +448,7 @@ def inner_run_cgi(self):
         xrw = self.headers.get('x-requested-with')
         if xrw:
             env['HTTP_X-REQUESTED-WITH'] = xrw
-        range = self.headers.getheader('range')
+        range = self.headers.get('range')
         if range:
             env['HTTP_RANGE'] = range