re.match in has_changed function never worked properly, because match
requires searched sequence to be present exactly at a start of processed
string, which is not the case here.
module.exit_json() does not like when the "changed" variable contains a
match object:
TypeError: <_sre.SRE_Match object at 0x81e2ae58> is not JSON serializable
Running the module with the argument "upgrade=yes" invokes an upgrade of
all installed packages.
While here clean up some comments.
Functionality requested by @qbit.
anatoly techtonik
Mikolaj Chwalisz
Paul Nicholson
Patrik Lundin
James Cammarata
Michael DeHaan