Add --releasever option to lorax-composer

If it isn't set the releasever value will use yum and the system / to
find the releasever.

src/pylorax/api/yumbase.py

@@ -72,6 +72,14 @@ def get_base_object(conf):
     if not os.path.isdir(yb.preconf.root):
         os.makedirs(yb.preconf.root)
 
+    _releasever = conf.get_default("composer", "releasever", None)
+    if not _releasever:
+        distroverpkg = ['system-release(releasever)', 'redhat-release']
+        # Use yum private function to guess the releasever
+        _releasever = yum.config._getsysver("/", distroverpkg)
+    log.info("releasever = %s", _releasever)
+    yb.preconf.releasever = _releasever
+
     # Turn on as much yum logging as we can
     yb.preconf.debuglevel = 6
     yb.preconf.errorlevel = 6

src/sbin/lorax-composer

@@ -55,6 +55,8 @@ def get_parser():
                         help="show program's version number and exit")
     parser.add_argument("-c", "--config", default="/etc/lorax/composer.conf", metavar="CONFIG",
                         help="Path to lorax-composer configuration file.")
+    parser.add_argument( "--releasever", default=None, metavar="STRING",
+                         help="Release version to use for $releasever in yum repository urls" )
     parser.add_argument("RECIPES", metavar="RECIPES",
                         help="Path to the recipes")
 
@@ -128,6 +130,10 @@ if __name__ == '__main__':
     server.config["GITLOCK"] = GitLock(repo=repo, lock=Lock(), dir=opts.RECIPES)
     server.config["COMPOSER_CFG"] = configure(conf_file=opts.config)
 
+    # If the user passed in a releasever set it in the configuration
+    if opts.releasever:
+        server.config["COMPOSER_CFG"].set("composer", "releasever", opts.releasever)
+
     # Get a YumBase to share with the requests
     yb = get_base_object(server.config["COMPOSER_CFG"])
     server.config["YUMLOCK"] = YumLock(yb=yb, lock=Lock())