Create BlockDeviceCmd object

This creates a BlockDeviceCmd object to hold the main() function.
This doesn't really do anything different right now, but sets a base
for using argparse subparsers to handle the command-line

Change-Id: I4acf95ff4d554a3b4e7e2244ab1706631b98458f

diskimage_builder/block_device/cmd.py

@@ -21,70 +21,77 @@ import yaml
 from diskimage_builder.block_device.blockdevice import BlockDevice
 from diskimage_builder import logging_config
 
+logger = logging.getLogger(__name__)
 
-def generate_phase_doc():
-    phase_doc = ""
-    bdattrs = dir(BlockDevice)
-    for attr in bdattrs:
-        if attr.startswith("cmd_"):
-            phase_doc += "  '" + attr[4:] + "'\n"
-            method = getattr(BlockDevice, attr, None)
-            # The first line is the line that is used
-            phase_doc += "    " + method.__doc__.split("\n")[0] + "\n"
-    return phase_doc
+
+class BlockDeviceCmd(object):
+
+    def generate_phase_doc(self):
+        phase_doc = ""
+        bdattrs = dir(BlockDevice)
+        for attr in bdattrs:
+            if attr.startswith("cmd_"):
+                phase_doc += "  '" + attr[4:] + "'\n"
+                method = getattr(BlockDevice, attr, None)
+                # The first line is the line that is used
+                phase_doc += "    " + method.__doc__.split("\n")[0] + "\n"
+        return phase_doc
+
+    def main(self):
+        logging_config.setup()
+        phase_doc = self.generate_phase_doc()
+
+        parser = argparse.ArgumentParser(
+            formatter_class=argparse.RawDescriptionHelpFormatter,
+            description="Create block device layer",
+            epilog="Available phases:\n" + phase_doc)
+        parser.add_argument('--phase', required=True,
+                            help="phase to execute")
+        parser.add_argument('--params', required=False,
+                            help="YAML file containing parameters for "
+                            "block-device handling.  Default is "
+                            "DIB_BLOCK_DEVICE_PARAMS_YAML")
+        parser.add_argument('--symbol', required=False,
+                            help="symbol to query for getval")
+        args = parser.parse_args()
+
+        # Find, open and parse the parameters file
+        if not args.params:
+            if 'DIB_BLOCK_DEVICE_PARAMS_YAML' in os.environ:
+                param_file = os.environ['DIB_BLOCK_DEVICE_PARAMS_YAML']
+            else:
+                parser.error(
+                    "DIB_BLOCK_DEVICE_PARAMS_YAML or --params not set")
+        else:
+            param_file = args.params
+            logger.info("params [%s]" % param_file)
+        try:
+            with open(param_file) as f:
+                params = yaml.safe_load(f)
+        except Exception:
+            logger.exception("Failed to open parameter YAML")
+            sys.exit(1)
+
+        logger.info("phase [%s]" % args.phase)
+
+        if args.symbol:
+            logger.info("symbol [%s]" % args.symbol)
+
+        bd = BlockDevice(params, args)
+
+        # Check if the method is available
+        method = getattr(bd, "cmd_" + args.phase, None)
+        if callable(method):
+            # If so: call it.
+            return method()
+        else:
+            logger.error("phase [%s] does not exists" % args.phase)
+            return 1
 
 
 def main():
-    logging_config.setup()
-    logger = logging.getLogger(__name__)
-    phase_doc = generate_phase_doc()
-
-    parser = argparse.ArgumentParser(
-        formatter_class=argparse.RawDescriptionHelpFormatter,
-        description="Create block device layer",
-        epilog="Available phases:\n" + phase_doc)
-    parser.add_argument('--phase', required=True,
-                        help="phase to execute")
-    parser.add_argument('--params', required=False,
-                        help="YAML file containing parameters for block-device"
-                        "handling.  Default is DIB_BLOCK_DEVICE_PARAMS_YAML")
-    parser.add_argument('--symbol', required=False,
-                        help="symbol to query for getval")
-    args = parser.parse_args()
-
-    # Find, open and parse the parameters file
-    if not args.params:
-        if 'DIB_BLOCK_DEVICE_PARAMS_YAML' in os.environ:
-            param_file = os.environ['DIB_BLOCK_DEVICE_PARAMS_YAML']
-        else:
-            parser.error("DIB_BLOCK_DEVICE_PARAMS_YAML or --params not set")
-    else:
-        param_file = args.params
-    logger.info("params [%s]" % param_file)
-    try:
-        with open(param_file) as f:
-            params = yaml.safe_load(f)
-    except Exception:
-        logger.exception("Failed to open parameter YAML")
-        sys.exit(1)
-
-    logger.info("phase [%s]" % args.phase)
-
-    if args.symbol:
-        logger.info("symbol [%s]" % args.symbol)
-
-    bd = BlockDevice(params, args)
-
-    # Check if the method is available
-    method = getattr(bd, "cmd_" + args.phase, None)
-    if callable(method):
-        # If so: call it.
-        return method()
-    else:
-        logger.error("phase [%s] does not exists" % args.phase)
-        return 1
-
-    return 0
+    bdc = BlockDeviceCmd()
+    return bdc.main()
 
 if __name__ == "__main__":
-    main()
+    sys.exit(main())