Provide --loglevel=PROGRESS for make VERBOSE=1

Provide --loglevel=PROGRESS for make VERBOSE=1

This provides enough information to diagnose problems in included
files while building the documentation.

[Dan Eble, 2020-01-27 02:52:44]

> This provides enough information to diagnose problems in included
> files while building the documentation.

LGTM, though I wonder why these problems (whatever they are) do not trigger
useful diagnostic messages at WARN or higher levels, which would be seen even at
the default verbosity level.  In other words, is this change just working around
deficiencies of the program?

[hanwenn, 2020-01-27 08:28:01]

On 2020/01/27 02:52:44, Dan Eble wrote:
> > This provides enough information to diagnose problems in included
> > files while building the documentation.
> 
> LGTM, though I wonder why these problems (whatever they are) do not trigger
> useful diagnostic messages at WARN or higher levels, which would be seen even
at
> the default verbosity level.  In other words, is this change just working
around
> deficiencies of the program?

kind of. If there is a problem with an input file, the progress messages would
tell you what
the last file processed was. 

The clean way to do this, is to catch the exception in python, annotate it with
the current file
and rethrow. It's more work, and this gets it done well enough for debugging.