charmhelper sync for vivid-kilo bug 1423680

hooks/charmhelpers/core/strutils.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# Copyright 2014-2015 Canonical Limited.
+#
+# This file is part of charm-helpers.
+#
+# charm-helpers is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# charm-helpers is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+
+import six
+
+
+def bool_from_string(value):
+    """Interpret string value as boolean.
+
+    Returns True if value translates to True otherwise False.
+    """
+    if isinstance(value, six.string_types):
+        value = six.text_type(value)
+    else:
+        msg = "Unable to interpret non-string value '%s' as boolean" % (value)
+        raise ValueError(msg)
+
+    value = value.strip().lower()
+
+    if value in ['y', 'yes', 'true', 't']:
+        return True
+    elif value in ['n', 'no', 'false', 'f']:
+        return False
+
+    msg = "Unable to interpret string value '%s' as boolean" % (value)
+    raise ValueError(msg)