SourceDescriptor-related bug

diff --cc Cython/Compiler/Errors.py
index 7a074052c4e4365497c3f31360ff6acea371f389,736d032615eaeb120b0e33042229ba71e7eff183..4c9e7981cf23026835643590798288885c3c2c1f
--- 1/Cython/Compiler/Errors.py
--- 2/Cython/Compiler/Errors.py
+++ b/Cython/Compiler/Errors.py
@@@ -42,7 -38,7 +42,7 @@@ class CompileWarning(PyrexWarning)
          self.position = position
          self.message = message
          if position:
--            pos_str = "%s:%d:%d: " % position
++            pos_str = "%s:%d:%d: " % (position[0].get_description(), position[1], position[2])
          else:
              pos_str = ""
          Exception.__init__(self, pos_str + message)