turn cythonize() error on unknown compilation options into a warning

CHANGES.rst

@@ -40,6 +40,13 @@ Bugs fixed
 
 * Allow arrays of C++ classes.
 
+Other changes
+-------------
+
+* Compilation no longer fails hard when unknown compilation options are passed.
+  Instead, it raises a warning and ignores them (as it did silently before 0.21).
+
+
 
 0.21 (2014-09-10)
 =================

Cython/Compiler/Main.py

@@ -498,9 +498,12 @@ class CompilationOptions(object):
         # ignore valid options that are not in the defaults
         unknown_options.difference_update(['include_path'])
         if unknown_options:
-            raise ValueError("got unexpected compilation option%s: %s" % (
+            # TODO: make this a hard error in 0.22
+            message = "got unknown compilation option%s, please remove: %s" % (
                 's' if len(unknown_options) > 1 else '',
-                ', '.join(unknown_options)))
+                ', '.join(unknown_options))
+            import warnings
+            warnings.warn(message)
 
         directives = dict(options['compiler_directives'])  # copy mutable field
         options['compiler_directives'] = directives