Throw correct error on creation of size 0

When trying to create an instance of size 0 an error is thrown
stating that the size was not specified, this is not correct
because I did specify it. The problem is that args.size evaluates
to False because size is 0.

This patch checks for size being zero instead and throws the correct
error message.

Change-Id: If00e83ccd919429dcfac7621dbbd9daa49f8b416

troveclient/tests/test_v1_shell.py

@@ -274,6 +274,10 @@ class ShellTest(utils.TestCase):
         self.run_command('cluster-force-delete cls-1234')
         self.assert_called('DELETE', '/clusters/cls-1234')
 
+    def test_boot_fail_with_size_0(self):
+        self.assertRaises(exceptions.ValidationError, self.run_command,
+                          'create test-member-1 1 --size 0 --volume_type lvm')
+
     def test_boot(self):
         self.run_command('create test-member-1 1 --size 1 --volume_type lvm')
         self.assert_called_anytime(

troveclient/v1/shell.py

@@ -521,7 +521,11 @@ def do_create(cs, args):
     """Creates a new instance."""
     flavor_id = _find_flavor(cs, args.flavor).id
     volume = None
-    if args.size:
+    if args.size is not None and args.size <= 0:
+        raise exceptions.ValidationError(
+            "Volume size '%s' must be an integer and greater than 0."
+            % args.size)
+    elif args.size:
         volume = {"size": args.size,
                   "type": args.volume_type}
     restore_point = None