This will be handled by env/superenv, not Python.

eql? should not depend on the hash value as hash values of uneql objects
can collide, but eql values may only collide for objects that are
actually eql.

Further, python dependencies are uniquely identified by the combination
of the name and imports attributes, so there is no reason to involved
the expensive binary computation for simple equality checks.

Fixes Homebrew/homebrew#20840.

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"...

Closes Homebrew/homebrew#20797.

So, `depends_on :fortran => :optional` will generate "--with-fortran"
rather than "--with-fortranRequired".

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.

* Fixes Homebrew/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.`

Closes Homebrew/homebrew#19998.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Exposing this as "to_a" was a mistake, versions are not arrays and it
causes incorrect behavior when splatted or using Kernel#Array(). Use the
more correct name "tokens" instead.

Closes Homebrew/homebrew#20357.

This allows formulae which won't build with Tiger's ld to conditionally
request a dependency on the ld64 formula. This modifies the build
environment appropriately, and will only be active on Tiger.

Authors should use `python.standard_caveats` instead.

* Accessor for python.binary
* Made `python.brewed?` more robust if no python found at all
* python.brewed? is more relaxed now and allows older versions
  of the Python formula.
* Only print about wrining sitecustomize.py and distutils.cfg if
verbose and debug.

* The python do ... end block does no longer
  require 'superenv' but saves and restores
  the ENV by using ENV.to_hash and `ensure`.
  This should resolve some build problems
  with formulae using `env :std`!
* `python_helper` is now in a module `Python`.
* Imporoved some comments in python_dependency.rb

This applies only to non-brewed python:
The user will still have to set his PYTHONPATH
in order to import python modules in an
external python interpreter. However, a
warning will be displayed, now.

Further, during the build, the PYTHONPATH
will be set to Homebrew's global site-packages
so that software (like PyQt and others) that
need to `import sipconfig` in python can
find the brewed sip and its python module.

Since Python has been removed from superenv and
added as an explicit `depends_on :python`,
we should add
`-F#{HOMEBREW_PREFIX}/opt/python/Framewoks`
so that build tools that don't use
`python-config --ldflags` (as they should!)
can link against brewed Python.

sys.version_info.major is only possible on 2.7+ or so.
Therefore, we now use [0] instead.

This reverts commit 9aaa89dbe832387249ab3ea4e22a8018cc9fe30a.

System python (for 2.x) does not provide `python2` binary.
So use `python` again.

For Python 3.x we still use `python3`.

To support system python on OS X

New `depends_on :python` Dependency.
New `depends_on :python3` Dependency.

To avoid having multiple formulae with endings -py2 and -py3,
we will handle support for different pythons (2.x vs. 3.x)
in the same formula.
Further brewed vs. external python will be transparently supported.

The formula also gets a new object `python`, which is false if
no Python is available or the user has disabled it. Otherwise
it is defined and provides several support methods:

python.site_packages # the site-packages in the formula's Cellar
python.global_site_packages
python.binary # the full path to the python binary
python.prefix
python.version
python.version.major
python.version.minor
python.xy # => e.g. "python2.7"
python.incdir # includes of python
python.libdir # the python dylib library
python.pkg_config_path # used internally by brew
python.from_osx?
python.framework?
python.universal?
python.pypy?
python.standard_caveats # Text to set PYTHONPATH for python.from_osx?
python.if3then3 # => "" for 2.x and to "3" for 3.x.

Further, to avoid code duplication, `python` takes an optional
block that is run twice if the formula defines depends_on
:python AND :python3.

python do
  system python, 'setup.py', "--prefix=#{prefix}"
end

Read more in the Homebrew wiki.

Closes Homebrew/homebrew#19966.

This allows default resolution of requirements without user intervention.

Closes Homebrew/homebrew#19627.

Fixes Homebrew/homebrew#19636.

By always passing around a single, unnested array rather than splatting
and then defensively flattening and compacting things, we can avoid
allocating a bunch of unnecessary arrays. This gives a performance boost
of roughly 4% when enumerating 2500 formulae, and has the side effect of
cleaning up the dependency API.

Fixes Homebrew/homebrew#18918.