[mm-common/wip/kjellahl/meson-build] util/build_scripts/doc-reference.py: Don't use feature from Python 3.7

[Kjell Ahlstedt <kjellahl src gnome org>]

commit c2e9ff1dd3fc820e5dc7aad1678e124b7fd820ef
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Tue Oct 8 13:23:41 2019 +0200

    util/build_scripts/doc-reference.py: Don't use feature from Python 3.7
    
    Don't use text=True in subprocess.run(). It does not exist in Python 3.5
    which is the Python version that mm-common requires.

 util/build_scripts/doc-reference.py | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)
---
diff --git a/util/build_scripts/doc-reference.py b/util/build_scripts/doc-reference.py
index c3d16b7..c798d48 100755
--- a/util/build_scripts/doc-reference.py
+++ b/util/build_scripts/doc-reference.py
@@ -38,14 +38,16 @@ def doxygen():
   # Relative paths in Doxyfile assume that Doxygen is run from the
   # build directory one level above Doxyfile.
   doxygen_cwd = os.path.join(doc_outdir, '..')
-  DOXYGEN = 'doxygen'
-  if ('DOXYGEN' in child_env) and child_env['DOXYGEN']:
-    DOXYGEN = child_env['DOXYGEN']
 
+  DOXYGEN = child_env.get('DOXYGEN', None)
+  if not DOXYGEN:
+    DOXYGEN = 'doxygen'
   doxygen_input = '@INCLUDE = ' + os.path.join('reference', 'Doxyfile') + '\n' \
                 + 'INPUT = "' + '" "'.join(sys.argv[4:]) + '"\n'
-  result = subprocess.run([DOXYGEN, '-'],
-    input=doxygen_input, text=True, env=child_env, cwd=doxygen_cwd)
+  # (Starting with Python 3.7 text=True is a more understandable equivalent to
+  # universal_newlines=True. Let's use only features in Python 3.5.)
+  result = subprocess.run([DOXYGEN, '-'], input=doxygen_input,
+    universal_newlines=True, env=child_env, cwd=doxygen_cwd)
   if result.returncode:
     return result.returncode