Comment 1 for bug 1469584

"""
       Additionally, the file names must conform to the
       filename requirements of run-parts: they must be entirely made up of
       letters, digits and can only contain the special signs underscores
       ('_') and hyphens ('-'). Any file that does not conform to these
       requirements will not be executed by run-parts. For example, any file
       containing dots will be ignored. This is done to prevent cron from
       running any of the files that are left by the Debian package management
       system when handling files in /etc/cron.d/ as configuration files (i.e.
       files ending in .dpkg-dist, .dpkg-orig, and .dpkg-new).
"""