Add --debug flag to python -mmatplotlib.dviread CLI.

The dviread module logs some information at the debug level (e.g., dvi
"specials").  Allow printing them from the CLI, to ease verification of
dvi internals.

Author: anntzer

lib/matplotlib/dviread.py

@@ -1347,8 +1347,12 @@ def _fontfile(cls, suffix, texname):
     parser = ArgumentParser()
     parser.add_argument("filename")
     parser.add_argument("dpi", nargs="?", type=float, default=None)
+    parser.add_argument("-d", "--debug", action="store_true")
     args = parser.parse_args()
 
+    if args.debug:
+        logging.basicConfig(level=logging.DEBUG)
+
     def _print_fields(*args):
         print(" ".join(map("{:>11}".format, args)))