doc/make.py of matplotlib-1.2.0rc2 has multiple except clauses that use "," instead of "as" (in the pre-v2.6 compatibility block) e.g.
except Error, err:
this is no longer supported in Python 3 and causes a syntax error.
Discussion in #1361 mentions some other files that need fixing, too.
Closing since #1383 and #1361 were closed/merged.