Make travis pass

Author: nwin

lib/matplotlib/backends/backend_pgf.py

@@ -317,7 +317,7 @@ def __init__(self):
                                      stdin=subprocess.PIPE,
                                      stdout=subprocess.PIPE,
                                      cwd=self.tmpdir)
-        except OSError, e:
+        except OSError as e:
             if e.errno == errno.ENOENT:
                 raise OSError(errno.ENOENT, "Latex command not found. "
                     "Install '%s' or change pgf.texsystem to the desired command."