In diagnostics, when directory is not writable, also hint to set permission.

[blankenberg]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

I don't want to admit how long it took me to notice the actual permission problem (/facepalm) with my (/user/local/sbin) directory, but it was preventing install of qemu, and I hope this will help the next person (who might be me again):

Warning: The following directories are not writable by your user:
/usr/local/sbin

You should change the ownership of these directories to your user.
  sudo chown -R $(whoami) /usr/local/sbin

And make sure that your user has write permission.
  chmod u+w /usr/local/sbin

[blankenberg]

Please let me know if there is something I should do for the failing test, but it looks unrelated, to me at least:

...
Step 9/9 : RUN HOMEBREW_NO_ANALYTICS=1 HOMEBREW_NO_AUTO_UPDATE=1 brew tap homebrew/core 	&& chown -R linuxbrew: /home/linuxbrew/.linuxbrew 	&& rm -rf ~/.cache
 ---> Running in 90b2fc031c0c
Error: ‌Running Homebrew as root is extremely dangerous and no longer supported.‌
As Homebrew does not drop privileges on installation you would be giving all
build scripts full access to your system.
Service 'sut' failed to build: The command '/bin/sh -c HOMEBREW_NO_ANALYTICS=1 HOMEBREW_NO_AUTO_UPDATE=1 brew tap homebrew/core 	&& chown -R linuxbrew: /home/linuxbrew/.linuxbrew 	&& rm -rf ~/.cache' returned a non-zero code: 1‌
##[error]Bash exited with code '1'.``

[blankenberg]

I see the tests are now passing (sweet) due to an upstream change, but it is possible that #5915 may have provided an alternative solution as well.

[MikeMcQuaid]

Thanks so much for your first contribution! Without people like you submitting PRs we couldn't run this project. You rock, @blankenberg!