Add context to the "Discarded Event" warning

[dd32]

The Discarding %s event warning is logged with the %s left as is, instead of replacing the expected context of which event is being discarded.

[coveralls]

Coverage remained the same at 99.846% when pulling ac98bdc on dd32:fix/missing-placeholder into 103ac00 on zigpy:dev.

[codecov-commenter]

Codecov Report

Merging #745 (ac98bdc) into dev (103ac00) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##              dev     #745   +/-   ##
=======================================
  Coverage   99.84%   99.84%           
=======================================
  Files          43       43           
  Lines        5844     5844           
=======================================
  Hits         5835     5835           
  Misses          9        9           

Impacted Files	Coverage Δ
zigpy/appdb.py	98.42% <100.00%> (ø)

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[puddly]

Thanks for the PR! It looks like Black is formatting the call to LOGGER.warning to take up three lines due to the trailing comma in the current zigpy codebase. Adding the second missing argument makes it like a "normal" function call and it can be condensed into a single line:

            LOGGER.warning("Discarding %s event", cb_name)

[dd32]

Thanks for the quick response and following that through @puddly and @Adminiuga!

I came back to follow up on the contributing guidelines & unit test failure only to find it was already done :)