Newsboat: Notify user if the podcast couldn't be renamed

[Minoru]

After downloading the podcast file, Podboat tries to rename it to remove the ".part" suffix. However, the return value of that call is never checked; if rename failed, the user won't know.

Problem flagged by Coverity Scan.

[ATM-SALEH]

I can pick up this one, if nobody is working on this issue

[Minoru]

@nick-cd considered working on this, but he's now busy with #1271, so I guess it's fine if you pick up this one.

[ATM-SALEH]

Apologies for responding after a long time. Had a quite busy few weeks.

I had a quick look at this one and have a question

If we get a non-zero return code from rename, should we update status to some value that indicates error (like, using dl->set_status(DlStatus::FAILED))? Or it should fail silently, without notifying the user?

[Minoru]

Hey, no problem! Yes, I think it should set the status to "failed", and display an error message in the status bar at the bottom of the screen.