When failing to find targets in an ignored directory, the error message should reflect the ignorance

[baroquebobcat]

This can be confusing to people. Especially if they use options that change the ignored paths.

For example, this command fails this way:

$ ./pants --pants-distdir=my-cool-project bundle my-cool-project/app:bin

Exception caught: (<class 'pants.build_graph.build_file_address_mapper.InvalidBuildFileReference'>)
Exception message: /<build-root-path>/my-cool-project/app does not contain any BUILD files.
  when translating spec my-cool-project/app:bin

If it instead said something like

$ ./pants --pants-distdir=my-cool-project bundle my-cool-project/app:bin

Failed to find BUILD files in `my-cool-project/app`. `my-cool-project` is ignored in /<build-root-path>.
  when translating spec my-cool-project/app:bin

[stuhood]

This is addressed in the new engine; would recommend tackling #3695 instead.

[baroquebobcat]

True. I meant to add that to the description. I filed this as a reminder to test for this scenario, since it's user facing.