Basic dependency checking. setup() has two new optional arguments

requires and provides. requires is a sequence of strings, of the
form 'packagename-version'. The dependency checking so far merely
does an '__import__(packagename)' and checks for packagename.__version__
You can also leave off the version, and any version of the package
will be installed.
There's a special case for the package 'python' - sys.version_info
is used, so
requires= ( 'python-2.3', )
just works.

Provides is of the same format as requires - but if it's not supplied,
a provides is generated by adding the version to each entry in packages,
or modules if packages isn't there.
Provides is currently only used in the PKG-INFO file. Shortly, PyPI
will grow the ability to accept these lines, and register will be
updated to send them.

There's a new command 'checkdep' command that runs these checks.
For this version, only greater-than-or-equal checking is done. We'll
add the ability to specify an optional operator later.

Lib/distutils/core.py

@@ -47,7 +47,8 @@ setup_keywords = ('distclass', 'script_name', 'script_args', 'options',
                   'name', 'version', 'author', 'author_email',
                   'maintainer', 'maintainer_email', 'url', 'license',
                   'description', 'long_description', 'keywords',
-                  'platforms', 'classifiers', 'download_url')
+                  'platforms', 'classifiers', 'download_url',
+                  'provides', 'requires', )
 
 # Legal keyword arguments for the Extension constructor
 extension_keywords = ('name', 'sources', 'include_dirs',