Check for HOMEBREW_PREFIX/share/python and python3
in PATH and tell about the new location and that
files from there can be removed. Also instructions
on how to upgrade python packages are given.
Some prefer to install with `--user` into their
home. For example to avoid `sudo` with system's
python. Now Homebrew can use those modules to
satisfy a python dependency on a certain module.
For example python and python3 both provide a
`Python.framework` and OS X Frameworks are made to
deal with this by putting them into `Versions` and
linking the default one as `Current`. However, brew
did not respect this and cleaned out stuff making
neither of the two versions work because `Current`
is replaced by an empty directory.
This commit fixes that. However, still one of the
two `Python.frameworks` has to remove it's
`Current` and `Headers` links, because brew cannot
decide alone which one is the "default" and allowed
to set the `Current` link.
A similar situation might apply to Qt 4 vs. 5..
* FixesHomebrew/homebrew#20572 by tweaking the logic that decides
which python is used by the `python` object
inside a formula. There was a bug when on 10.6
there is no Python 2.7 but a :recommended
Python was still treated as being available.
* Use the user's PATH when looking for an external
Python. Until now only brewed or OS X system's
python have been found by `depends_on :python`.
But now we support any Python in PATH (e.g.
pyenv's python).
* Further, instead of handling python modules
and import tests in LanguageModuleDependency,
these are now handled by:
depends_on :python => 'numpy' # for example
The old style
depends_on 'numpy' => :python
is still supported and is only an alias
for the newer style (only for :python, the
other languages are not altered by this commit).
The reasoning is that if a formula requires
a python module, it basically also needs
python itself - and further that specific
version of python has to provide the module.
So the `PythonInstalled` is the natural place
to check for the availability of a python
module.
Using a python module and other tags like
:optional or :recommended is done like so:
depends_on :python => [:optional, 'numpy']
Specifying another PyPi (Python Package index)
name than the module import name is seldom used
but supported, too:
depends_on :python => ['enchant'=>'pyenchant']
A last note: For clarity, you can define
multiple depends_on statements with different
modules to be importable.`
