avoid test failure
Use the POSIX character class instead of `\s` to match all whitespace in a
regular expression describing the language of valid inputs, in order to avoid a
test failure for the invalid escape sequence `\s` in Python strings.
@@ -531,7 +531,7 @@ class FfmpegBackend(Backend):
def _parse_float(self, line):
"""Extract a float from a key value pair in `line`.
- This format is expected: /[^:]:\s*value.*/, where `value` is
+ This format is expected: /[^:]:[[:space:]]*value.*/, where `value` is
the float.
"""
# extract value
