236a7beb34
Under Python 3.8, the following SyntaxWarning is logged on every
glanceclient invocation:
SyntaxWarning: "is not" with a literal. Did you mean "!="?
if kwargs.get('cacert', None) is not '':
Make use of '!=' rather than 'is not' to avoid this warning.
Change-Id: I11ed568932ec5ea0ffee629d6fd434433f262b67