osmupdate: retreave timestamp form .pbf file

[BrtBnn]

dowload.py tries to retrieve the latest timestamp from country.pbf using osmconvert country.pbf --out-timestamp.
If the country.pbf file does not have a timestamp and, osmconvert returns (invalid timestamp), download.py could recover the last-timestamp using osmconvert country.pbf --out-statistics, or is should throw an exception.

[Gustry]

Where did you get your PBF?
I always got a result from osmconvert country.pbf --out-timestamp in my case.

So if the timestamp is invalid, we should run osmconvert country.pbf --out-statistics ?

[olekyd]

if you download pbf file from http://download.openstreetmap.fr/extracts then osmconvert outputs (invalid timestamp), but if you download it from http://download.geofabrik.de then it's fine.