Python: Make Row's __getattr__ less error prone

Calling getattr() on a Row object after invoking delkey() with a value
that does not exist in the object will cause getattr() to fail with a
KeyError error. For example:

Oct 05 14:59:28 neutron-server[28435]:   File
"/usr/local/lib/python2.7/dist-packages/ovsdbapp/backend/ovs_idl/connection.py",
line 122, in run
Oct 05 14:59:28 neutron-server[28435]:
txn.results.put(txn.do_commit())
Oct 05 14:59:28 neutron-server[28435]:   File
"/usr/local/lib/python2.7/dist-packages/ovsdbapp/backend/ovs_idl/transaction.py",
line 86, in do_commit
Oct 05 14:59:28 neutron-server[28435]:     command.run_idl(txn)
Oct 05 14:59:28 neutron-server[28435]:   File
"/usr/local/lib/python2.7/dist-packages/ovsdbapp/backend/ovs_idl/command.py",
line 299, in run_idl
Oct 05 14:59:28 neutron-server[28435]:     if
isinstance(getattr(record, self.column), dict):
Oct 05 14:59:28 neutron-server[28435]:   File
"/usr/local/lib/python2.7/dist-packages/ovs/db/idl.py", line 843, in
__getattr__
Oct 05 14:59:28 neutron-server[28435]:     del dmap[key]
Oct 05 14:59:28 neutron-server[28435]: KeyError: 'bogusvalue'

This patch is replacing the "del dmap[key]" instruction with a
"dmap.pop(key, None)" instruction instead because a pop() (with a
default value) will not raise an exception in case the key does not
exist in the object in the first place, it will just ignore it.

Signed-off-by: Lucas Alvares Gomes <lucasagomes@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

python/ovs/db/idl.py

@@ -855,7 +855,7 @@ class Row(object):
                     if removes is not None:
                         for key in removes:
                             if key not in (inserts or {}):
-                                del dmap[key]
+                                dmap.pop(key, None)
                     datum = data.Datum.from_python(column.type, dmap,
                                                    _row_to_uuid)
             else: