tlsrpt-reportd not providing error indication when config file fetchers is invalid

[florianpiekert]

I had some typos in my config.file in the
[tlsrpt_reportd]
section.

the directive
fetchers = python3 /home/software/tlsrpt-reporter/tlsrpt_reporter/tlsrpt_fetcher.py --config_file=/etc/tlsrpt.conf
was not pointing to an existing file due to a typo in the directory name "-" instead of "_".

But, in reportd.log there was no indication of an error, which would be helpful to detect such mishaps (earlier).