Add --proxy to lorax-composer cmdline

Overrides the [dnf] proxy setting in the config file.

src/pylorax/api/config.py

@@ -58,6 +58,8 @@ def configure(conf_file="/etc/lorax/composer.conf", root_dir="/", test_config=Fa
     conf.set("repos", "use_system_repos", "1")
     conf.set("repos", "enabled", "*")
 
+    conf.add_section("dnf")
+
     if not test_config:
         # read the config file
         if os.path.isfile(conf_file):

src/sbin/lorax-composer

@@ -71,6 +71,8 @@ def get_parser():
                         help="Release version to use for $releasever in dnf repository urls")
     parser.add_argument("--tmp", default="/var/tmp",
                         help="Top level temporary directory")
+    parser.add_argument("--proxy", default=None, metavar="PROXY",
+                        help="Set proxy for DNF, overrides configuration file setting.")
     parser.add_argument("BLUEPRINTS", metavar="BLUEPRINTS",
                         help="Path to the blueprints")
 
@@ -230,6 +232,10 @@ if __name__ == '__main__':
     if opts.sharedir:
         server.config["COMPOSER_CFG"].set("composer", "share_dir", opts.sharedir)
 
+    # Override the config file's DNF proxy setting
+    if opts.proxy:
+        server.config["COMPOSER_CFG"].set("dnf", "proxy", opts.proxy)
+
     # Make sure the queue paths are setup correctly, exit on errors
     errors = make_queue_dirs(server.config["COMPOSER_CFG"], gid)
     if errors: