feat: expose library version at `google.auth.__version` (#683)
Move the version from `setup.py` to `google/auth/version.py`. Same as https://github.com/googleapis/python-api-core/pull/80. (see https://github.com/googleapis/python-api-core/issues/27 for motivation). This is option 3 in https://packaging.python.org/guides/single-sourcing-package-version/.
This unblocks a version check I'd like to add in https://github.com/googleapis/python-api-core/pull/134.
Usage:
```py
>>> import google.auth
>>> google.auth.__version__
'1.25.0'
```
diff --git a/google/auth/version.py b/google/auth/version.py
new file mode 100644
index 0000000..54ad932
--- /dev/null
+++ b/google/auth/version.py
@@ -0,0 +1,15 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+__version__ = "1.27.1"