chore(deps): bump python-novaclient from 18.11.0 to 18.12.0 (#1033)

Bumps [python-novaclient](https://docs.openstack.org/python-novaclient/latest) from 18.11.0 to 18.12.0.

---
updated-dependencies:
- dependency-name: python-novaclient
  dependency-version: 18.12.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -621,9 +621,9 @@ python-keystoneclient==5.6.0 \
     --hash=sha256:721de2aec7710076389c674ee27b6712e97d86c7e0ff487b0b4409c8fcee10e7 \
     --hash=sha256:86d5f615dac5b64797334c54a0440451aff11bea19328501df32e87385290702
     # via -r requirements.in
-python-novaclient==18.11.0 \
-    --hash=sha256:0a31ae20779d4cd171bb29c1fe4e6b22b9c7d97c79670db5149bbdfac03f57dc \
-    --hash=sha256:fc4ce032a6ce0fb911f4c640d260318d770ee171eedce7c12f887307fc24dc0c
+python-novaclient==18.12.0 \
+    --hash=sha256:ca70deb5f6b89c36a44df5abf62c67f41b2d35a1f906d3feba1716c1f056d26f \
+    --hash=sha256:ead3db2a3dd43a89bb5a56f62f87362a76e7ef9c01938699ff6c1a060f0e9eab
     # via -r requirements.in
 python-swiftclient==4.9.0 \
     --hash=sha256:0a53fd2fe27843108f39a1ff9e75dac253eeafb4c7e9e59d373263573f17665d \