Fix the bug of "openstack console log show"

The behaviors are inconsistent while different
negative line numbers specified.

Change-Id: I2573f3e789f5603c896758971830ffc0b94c5e2b
Closes-Bug: #1512263

1 files changed, 15 insertions, 0 deletions

diff --git a/openstackclient/common/parseractions.py b/openstackclient/common/parseractions.py
index 8f6008e2..fd90369a 100644
--- a/openstackclient/common/parseractions.py
+++ b/openstackclient/common/parseractions.py
@@ -65,3 +65,18 @@ class RangeAction(argparse.Action):
             # Too many values
             msg = "Invalid range, too many values"
             raise argparse.ArgumentError(self, msg)
+
+
+class NonNegativeAction(argparse.Action):
+    """A custom action to check whether the value is non-negative or not
+
+    Ensures the value is >= 0.
+    """
+
+    def __call__(self, parser, namespace, values, option_string=None):
+        try:
+            assert(int(values) >= 0)
+            setattr(namespace, self.dest, values)
+        except Exception:
+            msg = "%s expected a non-negative integer" % (str(option_string))
+            raise argparse.ArgumentTypeError(self, msg)