Invalid UTF-8 characters make the scanner crash

if the file is not UTF-8 formatted, but ISO or something like that, the scanner crashes:

ERROR: Could not build app org.documentfoundation.libreoffice due to unknown error: Traceback (most recent call last):
  File "/home/vagrant/fdroidserver/fdroidserver/build.py", line 1123, in main
    options.onserver, options.refresh):
  File "/home/vagrant/fdroidserver/fdroidserver/build.py", line 950, in trybuild
    build_local(app, build, vcs, build_dir, output_dir, srclib_dir, extlib_dir, tmp_dir, force, onserver, refresh)
  File "/home/vagrant/fdroidserver/fdroidserver/build.py", line 572, in build_local
    count = scanner.scan_source(build_dir, root_dir, build)
  File "/home/vagrant/fdroidserver/fdroidserver/scanner.py", line 203, in scan_source
    for line in f:
  File "/usr/lib/python3.4/codecs.py", line 313, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xdc in position 6238: invalid continuation byte
==== detail end ====
INFO: Finished.
INFO: 1 builds failed

The problem is not that the build fails but that it doesn't name the file while failing so that you can try to fix the error.