Bump requests-mock from 1.5.2 to 1.12.1

Bumps [requests-mock](https://github.com/jamielennox/requests-mock) from 1.5.2 to 1.12.1.
- [Release notes](https://github.com/jamielennox/requests-mock/releases)
- [Commits](jamielennox/requests-mock@1.5.2...1.12.1)

---
updated-dependencies:
- dependency-name: requests-mock
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

dev-requirements.txt

@@ -3,5 +3,5 @@ pytest-cov==2.6.0
 flake8==3.5.0
 pytest==3.8.2
 coveralls==1.5.1
-requests-mock==1.5.2
+requests-mock==1.12.1
 semver==2.8.1