commit f76d4525a was not actually working: extra keys from
config files are not yet into the config options dict at
import time. The fix is to move the logic inside the method,
like in `find_pg_tool` just below.
Also fix the use of `find_in_path` in report.py: the subprocess
may also raise AttributeError exception, so instead of listing
all the possible ones just re-raise the IOError shallowed by
`find_in_path` when the result is None.
Fixes#3809#3811
Simon Lejeune
467968b79a