Unhelpful error message on invalid source file or command

[julienrf]

Is your feature request related to a problem? Please describe.

When someone runs scala (as installed by cs install scala-experimental) with an invalid command name, or an invalid source file name, the output is not helpful:

$ scala foobar            

[error]  foobar: not found

Describe the solution you'd like

The tool should explain what it tried to do (here, running a Scala program named “foobar”), why it failed (here, the file “foobar” does not exist), and what the user could do to fix the problem (check that the file name is correct? add a missing extension? or, in case the user simply constructed a wrong invocation, remind them that they can get general help with scala --help?).

[Gedochao]

This is a duplicate of #1240.
Tagging #1240 as SIP and closing this.