Raise more useful error when tfm file is missing

jkseppan · jkseppan · commit a66b87f544dd · 2015-06-14T11:36:18.000+03:00
Fixes #4475
diff --git a/lib/matplotlib/dviread.py b/lib/matplotlib/dviread.py
@@ -396,6 +396,8 @@ def _xxx(self, special):
 
     def _fnt_def(self, k, c, s, d, a, l, n):
         tfm = _tfmfile(n[-l:].decode('ascii'))
+        if tfm is None:
+            raise FileNotFoundError("missing font metrics file: %s" % tfm)
         if c != 0 and tfm.checksum != 0 and c != tfm.checksum:
             raise ValueError('tfm checksum mismatch: %s'%n)
         # It seems that the assumption behind the following check is incorrect:
