chore: release 1.16.1 (#522)

:robot: I have created a release \*beep\* \*boop\* 
---
### [1.16.1](https://www.github.com/googleapis/google-auth-library-python/compare/v1.16.0...v1.16.1) (2020-06-04)


### Bug Fixes

* fix impersonated cred exception doc ([#521](https://www.github.com/googleapis/google-auth-library-python/issues/521)) ([9d5a9a9](https://www.github.com/googleapis/google-auth-library-python/commit/9d5a9a9884fecbd698a602d2a9fd9bec6b987de7))
* replace environment variable GCE_METADATA_ROOT with GCE_METADATA_HOST ([#433](https://www.github.com/googleapis/google-auth-library-python/issues/433)) ([8ffb4d3](https://www.github.com/googleapis/google-auth-library-python/commit/8ffb4d3e832607869026444e5a071c5f3e225fd2)), closes [#339](https://www.github.com/googleapis/google-auth-library-python/issues/339)
---


This PR was generated with [Release Please](https://github.com/googleapis/release-please).
diff --git a/setup.py b/setup.py
index 212228d..e02e9f9 100644
--- a/setup.py
+++ b/setup.py
@@ -30,7 +30,7 @@
 with io.open("README.rst", "r") as fh:
     long_description = fh.read()
 
-version = "1.16.0"
+version = "1.16.1"
 
 setup(
     name="google-auth",