Specify which test modules are being run in runtests.py

[AJ Collins]

I'm new to the project and was reviewing tests on a PR (​this one if that helps). I ran ./tests/runtests.py admin_scripts and thought it was running all the project's tests since it said "Found 238 test(s)". I naively thought 238 was too many tests for admin_scripts, and the output made no mention of "admin_scripts". I spent 5-10 minutes trying to see what I was doing wrong, since I was expecting the initial output to say *which* module was being run.

I'd like to propose that runtests.py specify the test module(s) being run *only when a subset is being run*. Proposed options below with changes surrounded in asterisks:

Option 1: List all modules being run. Potentially over-verbose when going beyond 10 modules...

> ./tests/runtests.py admin_scripts
Testing against Django installed in '/home/ajc/django' with up to 10 processes
Found 800 test(s). **Running tests in: admin_scripts, admin_views**.

Option 2: specify the number of modules being run:

> ./tests/runtests.py admin_scripts
Testing against Django installed in '/home/ajc/django' with up to 10 processes
Found 800 test(s) **across 2 module(s)**.

I'm mainly just hoping for some initial feedback from the test script indicating that I properly selected the subset of tests

[AJ Collins]

Actually might be more wise to keep this as a "read the docs" resolution (wontfix), since I was rushing. It's fairly high up on the Unit Tests doc :) ​https://docs.djangoproject.com/en/dev/internals/contributing/writing-code/unit-tests/#running-only-some-of-the-tests

[eddtsang]

./tests/runtests.py admin_scripts --verbosity 2

With verbosity 2, it will display the test name and which directory they are being pulled from.