add context to signature mangling errors

Author: amueller

numpydoc/numpydoc.py

@@ -113,8 +113,11 @@ def mangle_signature(app, what, name, obj, options, sig, retann):
 
     if not hasattr(obj, '__doc__'):
         return
-
-    doc = SphinxDocString(pydoc.getdoc(obj))
+    try:
+        doc = SphinxDocString(pydoc.getdoc(obj))
+    except ValueError as e:
+        filename = obj.__code__.co_filename
+        raise ValueError(str(e) + " in {}:{}".format(filename, name))
     sig = doc['Signature'] or getattr(obj, '__text_signature__', None)
     if sig:
         sig = re.sub(sixu("^[^(]*"), sixu(""), sig)