In 10.9 we'll probably have to use that code path
anyways and by now we have adapted all formulae
to be able to build on Xcode-only.

Enables new post-installation Cellar audit failures.

Closes Homebrew/homebrew#21242.

Perform post-installation checks if a formula is installed.
Added for brew test-bot to be able to fail on bad Cellar installation.

LanguageModuleDependency.new(:python,...) is deprecated now.
Replace it by
    depends_on :python => ['module' => 'name-on-PyPi']

Note, in the explict form:

    PythonInstalled.new('2.7') => :recommended

the tag :recommended is ignored (not a limitation
of PythonInstalled itself). One solution was to write

    PythonInstalled.new('2.7', [:recommended])

but that is not as beautiful as we like it.

Therefore, now it is possible to:

    depends_on :python => ['2.7', :recommended]

Only the first tag is attempted to be parsed as
a version specifyer "x" or "x.y" or "x.y.z"...

Since e1c62c35465eb6149688c745e4309438c08c410b, we exit early if the
outdated array is empty, so we no longer need to check this before
proceeding.

Only run the `python do ... end` loop once even if
multiple `depends_on :python => 'module-name'` are
present.

As documented in the man page, when given no arguments, `brew search`
will list all formulae. This is different than giving an *empty*
argument.

Closes Homebrew/homebrew#21216.

Fixes Homebrew/homebrew#19475.
Fixes Homebrew/homebrew#21184.

All core formulae have been migrated to .io addresses except
for software maintained by github itself.

Closes Homebrew/homebrew#21163.

Closes Homebrew/homebrew#21070.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Now that this is handled by a Requirement with a default formula, this
code cannot be triggered under normal circumstances.

The advice given has now been moved to the Formula Cookbook on the wiki.

Closes Homebrew/homebrew#21060.

Closes Homebrew/homebrew#21113.