Bug#870310: glib-mkenums: UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 108: ordinal not in range(128)

[Adrian Bunk]

Package: libglib2.0-dev-bin
Version: 2.53.4-2
Severity: grave
Control: affects -1 src:gthumb

https://tests.reproducible-builds.org/debian/rb-pkg/unstable/i386/gtk2-engines-xfce.html
https://buildd.debian.org/status/package.php?p=gthumb&suite=sid

...
Found cached translation database
Merging translations into gthumb-import.desktop.
Traceback (most recent call last):
  File "/usr/bin/glib-mkenums", line 669, in <module>
    process_file(fname)
  File "/usr/bin/glib-mkenums", line 406, in process_file
    line = curfile.readline()
  File "/usr/lib/python3.5/encodings/ascii.py", line 26, in decode
    return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 108: ordinal not in range(128)
Found cached translation database
Merging translations into gthumb.desktop.
Makefile:963: recipe for target 'org.gnome.gthumb.enums.xml' failed
make[4]: *** [org.gnome.gthumb.enums.xml] Error 1