Now the default python version of rawhide has been upgraded to
python 3.7.4, this patch fixes those py2->py3 issues which followed
from the origin heat-agent commits[1][2].
[1] 25cd394bbe
[2] 73e2125532
Task: 35989
Story: 2006283
Change-Id: I23056513dcc6f0cb0c7d41aa529f6a2e77679db9
bd23e58825