def gem(b, r):
    logging.info('searching for Ruby gems')

    # Precompile a pattern for extracting the version of Ruby that was used
    # to install the gem.
    pattern = re.compile(r'gems/([^/]+)/gems')

    # Look for gems in all the typical places.  This is easier than looking
    # for `gem` commands, which may or may not be on `PATH`.
    for globname in ('/usr/lib/ruby/gems/*/gems',
                     '/usr/local/lib/ruby/gems/*/gems',
                     '/var/lib/gems/*/gems'):
        for dirname in glob.glob(globname):

            # The `ruby1.9.1` (really 1.9.2) package on Maverick begins
            # including RubyGems in the `ruby1.9.1` package and marks the
            # `rubygems1.9.1` package as virtual.  So for Maverick and
            # newer, the manager is actually `ruby1.9.1`.
            match = pattern.search(dirname)
            if '1.9.1' == match.group(1) and util.rubygems_virtual():
                manager = 'ruby{0}'.format(match.group(1))

            # Oneiric and RPM-based distros just have one RubyGems package.
            elif util.rubygems_unversioned():
                manager = 'rubygems'

            # Debian-based distros qualify the package name with the version
            # of Ruby it will use.
            else:
                manager = 'rubygems{0}'.format(match.group(1))

            for entry in os.listdir(dirname):
                try:
                    package, version = entry.rsplit('-', 1)
                except __HOLE__:
                    logging.warning('skipping questionably named gem {0}'.
                                    format(entry))
                    continue
                if not r.ignore_package(manager, package):
                    b.add_package(manager, package, version)
dataset/ETHPy150Open devstructure/blueprint/blueprint/backend/gem.py/gem