Raise user-friendly exceptions in str2dict

Currently str2dict raises non user-friendly exceptions when input is not
valid:

  neutron subnet-create mynetwork 10/23 --allocation-pools=10/24
  # implies str2dict('10/24')
  # raises:
     dictionary update sequence element #0 has length 1; 2 is required

This change updates str2dict implementation in order to raise
user-friendly exceptions.

Closes-Bug: #1460336
Change-Id: Id381865e6e5d9bebcb2c984c0338126566a97c2b

neutronclient/common/utils.py

@@ -105,9 +105,15 @@ def str2dict(strdict):
 
     :param strdict: key1=value1,key2=value2
     """
-    if not strdict:
+    result = {}
-        return {}
+    if strdict:
-    return dict([kv.split('=', 1) for kv in strdict.split(',')])
+        for kv in strdict.split(','):
+            key, sep, value = kv.partition('=')
+            if not sep:
+                msg = _("invalid key-value '%s', expected format: key=value")
+                raise argparse.ArgumentTypeError(msg % kv)
+            result[key] = value
+    return result
 
 
 def http_log_req(_logger, args, kwargs):

neutronclient/tests/unit/test_utils.py

@@ -13,6 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import argparse
+
 import testtools
 
 from neutronclient.common import exceptions
@@ -42,6 +44,11 @@ class TestUtils(testtools.TestCase):
         expected = {}
         self.assertEqual(expected, utils.str2dict(input_str))
 
+    def test_invalid_string_to_dictionary(self):
+        input_str = 'invalid'
+        self.assertRaises(argparse.ArgumentTypeError,
+                          utils.str2dict, input_str)
+
     def test_get_dict_item_properties(self):
         item = {'name': 'test_name', 'id': 'test_id'}
         fields = ('name', 'id')