Without the filename it can be cumbersome to find which file caused
the error
user@apertis:~/apertis-tests$ make check
misc/syntax-check.py
Traceback (most recent call last):
  File misc/syntax-check.py, line 56, in <module>
    check_jinja2_template(template)
  File misc/syntax-check.py, line 34, in check_jinja2_template
    expanded_file = env.get_template(filename).render()
  File /usr/lib/python3/dist-packages/jinja2/environment.py, line 812, in get_template
    return self._load_template(name, self.make_globals(globals))
  File /usr/lib/python3/dist-packages/jinja2/environment.py, line 774, in _load_template
    cache_key = self.loader.get_source(self, name)[1]
  File /usr/lib/python3/dist-packages/jinja2/loaders.py, line 175, in get_source
    contents = f.read().decode(self.encoding)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x87 in position 16: invalid start byte
Makefile:76: recipe for target 'check' failed
make: *** [check] Error 1

Replace that ugly traceback with a more comprehensive output:
user@apertis:~/apertis-tests$ ./misc/syntax-check.py
Exception 'utf-8' codec can't decode byte 0x87 in position 16: invalid start byte when checking .common-boot-tpl.yaml.swp

Signed-off-by: Frédéric Dalleau <frederic.dalleau@collabora.com>