Feature request: Print a message if module can't connect to input interface

[vaclavbartos]

If I run a module (e.g. logger) manually from a terminal and don't see any data coming, it's not obvious whether there are actually no data on the input interface, or the module can't connect to it, e.g. because of a wrong interface name used.

I know there are ways to determine the status of each interface, e.g. using -vvv or supcli -x, but none of it is practical for the common case of testing something by running modules from a terminal. An explicit message from the module would be much more user-friendly.

I propose the following:
If the input interface (any of them) fails to establish a connection AND stderr is a tty, print a message to stderr (e.g. "Can't connect to {ifc}, retrying ...").

Ideally also with a reason why it can't connect (e.g. unix-socket with such name doesn't exist, tcp connection refused, incompatible data format) and with a "connected" message when it connects succesfully afterwards.

I think it souldn't break anything, since it will print messaes only to terminal, and it would make testing/debugging much easier.