pylint: say what you're missing.

The binary can be specified and probably you'll need something
different if you specified something other than pylint.

Fall back to suggesting the name of the binary which happens to match
the package name, for pylint3.

Bug: 78321780
Test: ./pylint.py --executable-path asdf ./pylint.py
  # and observe the error message.

Change-Id: If93726d9bbd097f97ccfe132404a9cb2cabcb033