Fix backend_pgf header.

anntzer · anntzer · commit 07856d833672 · 2019-05-08T02:38:16.000+02:00
At least in some cases (i.e. locally...), tex appears to treat a first
line of `% TeX program = ...` passed to its stdin as an empty filename
followed by a comment, leading to a crash ("I can't find file ''").

Fix that by moving the comment to the second line.
diff --git a/lib/matplotlib/backends/backend_pgf.py b/lib/matplotlib/backends/backend_pgf.py
@@ -212,9 +212,10 @@ def _build_latex_header():
         # fonts later when we don't expect the additional output on stdout.
         # TODO: is this sufficient?
         latex_header = [
+            r"\documentclass{minimal}",
             # Include TeX program name as a comment for cache invalidation.
+            # TeX does not allow this to be the first line.
             r"% !TeX program = {}".format(rcParams["pgf.texsystem"]),
-            r"\documentclass{minimal}",
             latex_preamble,
             latex_fontspec,
             r"\begin{document}",
