Previously, using --property-filter with invalid arguments resulted in
a rather cryptic error message:
$ glance image-list --property-filter name
dictionary update sequence element #0 has length 1; 2 is required
Now, something which is human decipherable is printed:
$ glance image-list --property-filter name
Argument --property-filter requires properties in the format KEY=VALUE
Change-Id: I61d19894fd8864bdca2fa3f627da3c7eb1341c51