SongPro import fails with traceback

[Tomas Groth]

Original reported in https://support.openlp.org/scp/tickets.php?id=3443 including sample file.

Trying to import the file causes this traceback:
Traceback (most recent call last):
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/core/ui/lib/wizard.py", line 219, in on_current_id_changed
    self.perform_wizard()
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/plugins/songs/forms/songimportform.py", line 351, in perform_wizard
    importer.do_import()
  File "/home/tgc/projects/OpenLP/code/trunk/openlp/plugins/songs/lib/importers/songpro.py", line 79, in do_import
    for file_line in songs_file:
  File "/usr/lib/python3.5/codecs.py", line 321, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe8 in position 5239: invalid continuation byte