From 25e4eaef483716decb4e1510ec675b22c4d7400a Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Sat, 24 Nov 2018 23:21:24 +0100
Subject: [PATCH] Write error messages to logger instead of stderr

---
 lib/matplotlib/afm.py                  | 12 +++++++-----
 lib/matplotlib/backends/backend_pdf.py | 13 +++----------
 lib/matplotlib/backends/backend_pgf.py |  4 ++--
 3 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/lib/matplotlib/afm.py b/lib/matplotlib/afm.py
index 3db8442e8de7..321a33ade7f1 100644
--- a/lib/matplotlib/afm.py
+++ b/lib/matplotlib/afm.py
@@ -38,13 +38,17 @@
 """
 
 from collections import namedtuple
+import logging
 import re
-import sys
+
 
 from ._mathtext_data import uni2type1
 from matplotlib.cbook import deprecated
 
 
+_log = logging.getLogger(__name__)
+
+
 # some afm files have floats where we are expecting ints -- there is
 # probably a better way to handle this (support floats, round rather
 # than truncate).  But I don't know what the best approach is now and
@@ -160,12 +164,10 @@ def _parse_header(fh):
         try:
             d[key] = headerConverters[key](val)
         except ValueError:
-            print('Value error parsing header in AFM:', key, val,
-                  file=sys.stderr)
+            _log.error('Value error parsing header in AFM: %s, %s', key, val)
             continue
         except KeyError:
-            print('Found an unknown keyword in AFM header (was %r)' % key,
-                  file=sys.stderr)
+            _log.error('Found an unknown keyword in AFM header (was %r)' % key)
             continue
         if key == b'StartCharMetrics':
             return d
diff --git a/lib/matplotlib/backends/backend_pdf.py b/lib/matplotlib/backends/backend_pdf.py
index 98a559c836bd..aa1b8bdd5fc6 100644
--- a/lib/matplotlib/backends/backend_pdf.py
+++ b/lib/matplotlib/backends/backend_pdf.py
@@ -1520,23 +1520,16 @@ def writeObject(self, object, contents):
 
     def writeXref(self):
         """Write out the xref table."""
-
         self.startxref = self.fh.tell() - self.tell_base
         self.write(b"xref\n0 %d\n" % self.nextObject)
-        i = 0
-        borken = False
-        for offset, generation, name in self.xrefTable:
+        for i, (offset, generation, name) in enumerate(self.xrefTable):
             if offset is None:
-                print('No offset for object %d (%s)' % (i, name),
-                      file=sys.stderr)
-                borken = True
+                raise AssertionError(
+                    'No offset for object %d (%s)' % (i, name))
             else:
                 key = b"f" if name == 'the zero object' else b"n"
                 text = b"%010d %05d %b \n" % (offset, generation, key)
                 self.write(text)
-            i += 1
-        if borken:
-            raise AssertionError('Indirect object does not exist')
 
     def writeInfoDict(self):
         """Write out the info dictionary, checking it for good form"""
diff --git a/lib/matplotlib/backends/backend_pgf.py b/lib/matplotlib/backends/backend_pgf.py
index cd14794d7ce8..c1fa91e6c765 100644
--- a/lib/matplotlib/backends/backend_pgf.py
+++ b/lib/matplotlib/backends/backend_pgf.py
@@ -756,10 +756,10 @@ def add(tmpdir):
     @staticmethod
     def cleanup_remaining_tmpdirs():
         for tmpdir in TmpDirCleaner.remaining_tmpdirs:
+            error_message = "error deleting tmp directory {}".format(tmpdir)
             shutil.rmtree(
                 tmpdir,
-                onerror=lambda *args: print("error deleting tmp directory %s"
-                                            % tmpdir, file=sys.stderr))
+                onerror=lambda *args: _log.error(error_message))
 
 
 class FigureCanvasPgf(FigureCanvasBase):