Add support for the GCLOUD_PROJECT environment variable (#73)
diff --git a/google/auth/environment_vars.py b/google/auth/environment_vars.py
index 9785c34..b4ed2b2 100644
--- a/google/auth/environment_vars.py
+++ b/google/auth/environment_vars.py
@@ -22,6 +22,13 @@
environment variable is also used by the Google Cloud Python Library.
"""
+LEGACY_PROJECT = 'GCLOUD_PROJECT'
+"""Previously used environment variable defining the default project.
+
+This environment variable is used instead of the current one in some
+situations (such as Google App Engine).
+"""
+
CREDENTIALS = 'GOOGLE_APPLICATION_CREDENTIALS'
"""Environment variable defining the location of Google application default
credentials."""