Python 2.x and 3.x support

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.

1 files changed, 7 insertions, 4 deletions

diff --git a/Library/Formula/pygobject.rb b/Library/Formula/pygobject.rb
index 969950389..f60ebb54c 100644
--- a/Library/Formula/pygobject.rb
+++ b/Library/Formula/pygobject.rb
@@ -7,6 +7,7 @@ class Pygobject < Formula
 
   depends_on 'pkg-config' => :build
   depends_on 'glib'
+  depends_on :python
 
   option :universal
 
@@ -17,9 +18,11 @@ class Pygobject < Formula
 
   def install
     ENV.universal_binary if build.universal?
-    system "./configure", "--disable-dependency-tracking",
-                          "--prefix=#{prefix}",
-                          "--disable-introspection"
-    system "make install"
+    python do
+      system "./configure", "--disable-dependency-tracking",
+                            "--prefix=#{prefix}",
+                            "--disable-introspection"
+      system "make install"
+    end
   end
 end