WSGITask: Patch should be enabled only if waitress egg is available

product/ERP5Type/patches/WSGITask.py

 # -*- coding: utf-8 -*-
 
 import ZPublisher.HTTPRequest
-from waitress.task import WSGITask
+try:
+  from waitress.task import WSGITask
+except ImportError:
+  WSGITask = None
 
-WSGITask_get_environment = WSGITask.get_environment
+# Patch should be enabled only if waitress egg is available
+if WSGITask is not None:
+  WSGITask_get_environment = WSGITask.get_environment
 
-def get_environment(self):
-  if ZPublisher.HTTPRequest.trusted_proxies == ('0.0.0.0',): # Magic value to enable this functionality
-    # Frontend-facing proxy is responsible for sanitising
-    # X_FORWARDED_FOR, and only trusted accesses should bypass
-    # that proxy. So trust first entry.
-    forwarded_for = dict(self.request.headers).get('X_FORWARDED_FOR', '').split(',', 1)[0].strip()
-  else:
-    forwarded_for = None
+  def get_environment(self):
+    if ZPublisher.HTTPRequest.trusted_proxies == ('0.0.0.0',): # Magic value to enable this functionality
+      # Frontend-facing proxy is responsible for sanitising
+      # X_FORWARDED_FOR, and only trusted accesses should bypass
+      # that proxy. So trust first entry.
+      forwarded_for = dict(self.request.headers).get('X_FORWARDED_FOR', '').split(',', 1)[0].strip()
+    else:
+      forwarded_for = None
 
-  environ = WSGITask_get_environment(self)
+    environ = WSGITask_get_environment(self)
 
-  if forwarded_for:
-    environ['REMOTE_HOST'] = environ['REMOTE_ADDR'] = forwarded_for
+    if forwarded_for:
+      environ['REMOTE_HOST'] = environ['REMOTE_ADDR'] = forwarded_for
 
-  return environ
+    return environ
 
-WSGITask.get_environment = get_environment
+  WSGITask.get_environment = get_environment