These tests cover a few aspects of the `FormulaAuditor#audit_deps`
method. The main focus is the part where FormulaAuditor checks for
dependencies on formulas which are tagged `keg_only` with the
`:provided_by_macos` reason.
For this particular kind of `keg_only` formulas, we expect
`brew audit --new-formula` to fail with a problem message like:
> Dependency 'bc' may be unnecessary as it is provided by
> macOS; try to build this formula without it.
For more details, see the relevant discussion:
[1] https://github.com/Homebrew/homebrew-core/pull/14067#issuecomment-335046151
[2] https://github.com/Homebrew/brew/pull/3290#issuecomment-335052140
Another attempt at fixing `brew audit` issues around detecting
`revision` and `version_scheme` changes correctly. First done in #1754
and #2086 (reverted in #2099 and #2100).
To ease future debugging a `ph` helper has been added to print a hash
and a series of RSpec tests to verify that the `revision`,
`version_scheme` and `version` formula version audits behave as
expected.
Fixes#1731.
