buildd update to Python 3 broke some python scripts

seen in a groovy test rebuild, however that is not limited to test rebuilds.

https://launchpadlibrarian.net/499441237/buildlog_ubuntu-groovy-ppc64el.bash_5.0-6ubuntu2_BUILDING.txt.gz

run-glob-test
Traceback (most recent call last):
  File "/usr/share/launchpad-buildd/bin/check-implicit-pointer-functions", line 33, in <module>
    sys.exit(main())
  File "/usr/share/launchpad-buildd/bin/check-implicit-pointer-functions", line 25, in main
    problems = filter_log(sys.stdin, sys.stdout, in_line=args.inline)
  File "/usr/lib/python3/dist-packages/lpbuildd/check_implicit_pointer_functions.py", line 64, in filter_log
    line = in_file.readline()
  File "/usr/lib/python3.6/codecs.py", line 321, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xa3 in position 547: invalid start byte
Warning: unable to close filehandle properly: Broken pipe, <STDIN> line 5900 during global destruction.