- access times are likely to differ, a race condition is possible
- stat() has be done after the change to be able to compare
- comments added
- force sync after modifying test file
- make code easier to understand
See https://github.com/metabrainz/picard/pull/1132#issuecomment-474113665
https://docs.python.org/3/library/os.html#os.utime
Since Python 3.3, ns parameter is available
"The best way to preserve exact times is to use the st_atime_ns and st_mtime_ns
fields from the os.stat() result object with the ns parameter to utime."
Make time preservation testable.
