[PATCH 3/3] docs: sphinx/kfigure.py: Redirect warnings from inkscape to /dev/null

[Akira Yokosawa <akiyks@gmail.com>]

Depending on its version, distro config, and system-setup type,
inkscape(1) emits various warning messages which are harmless in
command-line uses.

List of such warning messages (incomplete, long ones wrapped):

  o Gtk-Message: hh:mm:ss.nnn: Failed to load module "canberra-gtk-module"
  o Unable to init server: Could not connect: Connection refused
  o Failed to get connection
  o ** (inkscape:xxx): CRITICAL **: hh:mm:ss.nnn: dbus_g_proxy_new_for_name:
    assertion 'connection != NULL' failed
  o ** (inkscape:xxx): CRITICAL **: hh:mm:ss.nnn: dbus_g_proxy_call:
    assertion 'DBUS_IS_G_PROXY (proxy)' failed
  o ** (inkscape:xxx): CRITICAL **: hh:mm:ss.nnn: dbus_g_connection_register_g_object:
    assertion 'connection != NULL' failed
  o ** (inkscape:xxx): WARNING **: hh:mm:ss.nnn:
    Fonts dir '/usr/share/inkscape/fonts' does not exist and will be ignored.

To avoid unnecessary anxiety, redirect warning messages from inkscape(1)
to /dev/null by default.

The redirection can be disabled by setting SPHINX_SHOW_INKSCAPE_WARN, e.g.,:

    make SPHINX_SHOW_INKSCAPE_WARN=1 pdfdocs

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
---
 Documentation/sphinx/kfigure.py | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/Documentation/sphinx/kfigure.py b/Documentation/sphinx/kfigure.py
index 8d7c59e52ceb..d5802e3975e5 100644
--- a/Documentation/sphinx/kfigure.py
+++ b/Documentation/sphinx/kfigure.py
@@ -124,6 +124,9 @@ rsvg_convert_cmd = None
 inkscape_cmd = None
 # Inkscape prior to 1.0 uses different command options
 inkscape_ver_one = False
+# Show warning from inkscape(1), enabled by setting env var
+# SPHINX_SHOW_INKSCAPE_WARN
+inkscape_show_warn = False
 
 
 def setup(app):
@@ -173,7 +176,7 @@ def setupTools(app):
     This function is called once, when the builder is initiated.
     """
     global dot_cmd, convert_cmd, rsvg_convert_cmd   # pylint: disable=W0603
-    global inkscape_cmd, inkscape_ver_one  # pylint: disable=W0603
+    global inkscape_cmd, inkscape_ver_one, inkscape_show_warn  # pylint: disable=W0603
     kernellog.verbose(app, "kfigure: check installed tools ...")
 
     dot_cmd = which('dot')
@@ -188,12 +191,19 @@ def setupTools(app):
                        "graphviz from https://www.graphviz.org")
     if inkscape_cmd:
         kernellog.verbose(app, "use inkscape(1) from: " + inkscape_cmd)
-        inkscape_ver = subprocess.check_output([inkscape_cmd, '--version'])
+        inkscape_ver = subprocess.check_output([inkscape_cmd, '--version'],
+                                               stderr=subprocess.DEVNULL)
         ver_one_ptn = b'Inkscape 1'
         inkscape_ver_one = re.search(ver_one_ptn, inkscape_ver)
         convert_cmd = None
         rsvg_convert_cmd = None
 
+        try:
+            if os.environ['SPHINX_SHOW_INKSCAPE_WARN']:
+                inkscape_show_warn = True
+        except KeyError:
+            pass
+
     else:
         if convert_cmd:
             kernellog.verbose(app, "use convert(1) from: " + convert_cmd)
@@ -360,7 +370,11 @@ def svg2pdf(app, svg_fname, pdf_fname):
             cmd = [inkscape_cmd, '-z', '--export-pdf=%s' % pdf_fname, svg_fname]
 
     # use stdout and stderr from parent
-    exit_code = subprocess.call(cmd)
+    if inkscape_show_warn:
+        exit_code = subprocess.call(cmd)
+    else:
+        exit_code = subprocess.call(cmd, stderr=subprocess.DEVNULL)
+
     if exit_code != 0:
         kernellog.warn(app, "Error #%d when calling: %s" % (exit_code, " ".join(cmd)))
     return bool(exit_code == 0)
-- 
2.17.1