@@ -80,7 +80,7 @@ for file in samples/**/requirements.txt; do
 EXIT=$?
 
 # If this is a periodic build, send the test log to the FlakyBot.
-# See https://.com/googleapis/repo-automation-bots/tree/master/packages/flakybot.
+# See https://.com/googleapis/repo-automation-bots/tree/main/packages/flakybot.
 if [[ $KOKORO_BUILD_ARTIFACTS_SUBDIR = *"periodic"* ]]; then
 chmod +x $KOKORO_GFILE_DIR/linux_amd64/flakybot
 $KOKORO_GFILE_DIR/linux_amd64/flakybot

@@ -49,9 +49,9 @@ You'll have to create a development environment using a Git checkout:
 # Configure remotes such that you can pull changes from the googleapis/python-api-core
 # repository into your local repository.
 $ git remote add upstream [email protected]:googleapis/python-api-core.git
-# fetch and merge changes from upstream into master
+# fetch and merge changes from upstream into main
 $ git fetch upstream
-$ git merge upstream/master
+$ git merge upstream/main
 
 Now your local repo is set up such that you will push changes to your
 repo, from which you can submit a pull request.
@@ -109,12 +109,12 @@ Coding Style
 variables::
 
 export GOOGLE_CLOUD_TESTING_REMOTE="upstream"
-export GOOGLE_CLOUD_TESTING_BRANCH="master"
+export GOOGLE_CLOUD_TESTING_BRANCH="main"
 
 By doing this, you are specifying the location of the most up-to-date
 version of ``python-api-core``. The the suggested remote name ``upstream``
 should point to the official ``googleapis`` checkout and the
-the branch should be the main branch on that remote (``master``).
+the branch should be the main branch on that remote (``main``).
 
 - This repository contains configuration for the
 `pre-commit <https://pre-commit.com/>`__ tool, which automates checking
@@ -185,7 +185,7 @@ The `description on PyPI`_ for the project comes directly from the
 ``README``. Due to the reStructuredText (``rst``) parser used by
 PyPI, relative links which will work on (e.g. ``CONTRIBUTING.rst``
 instead of
-``https://.com/googleapis/python-api-core/blob/master/CONTRIBUTING.rst``)
+``https://.com/googleapis/python-api-core/blob/main/CONTRIBUTING.rst``)
 may cause problems creating links or rendering the description.
 
 .. _description on PyPI: https://pypi.org/project/google-api-core
@@ -210,7 +210,7 @@ We support:
 
 Supported versions can be found in our ``noxfile.py`` `config`_.
 
-.. _config: https://.com/googleapis/python-api-core/blob/master/noxfile.py
+.. _config: https://.com/googleapis/python-api-core/blob/main/noxfile.py
 
 
 We also explicitly decided to support Python 3 beginning with version 3.6.

@@ -293,8 +293,7 @@ class Cancelled(ClientError):
 """Exception mapping a :attr:`grpc.StatusCode.CANCELLED` error."""
 
 # This maps to HTTP status code 499. See
-# https://.com/googleapis/googleapis/blob/master/google/rpc\
-# /code.proto
+# https://.com/googleapis/googleapis/blob/master/google/rpc/code.proto
 code = 499
 grpc_status_code = grpc.StatusCode.CANCELLED if grpc is not None else None
 

@@ -43,8 +43,10 @@ class AsyncFuture(base.Future):
 The :meth:`done` method should be implemented by subclasses. The polling
 behavior will repeatedly call ``done`` until it returns True.
 
-.. note: Privacy here is intended to prevent the final class from
-overexposing, not to prevent subclasses from accessing methods.
+.. note::
+
+Privacy here is intended to prevent the final class from
+overexposing, not to prevent subclasses from accessing methods.
 
 Args:
 retry (google.api_core.retry.Retry): The retry configuration used

@@ -29,7 +29,17 @@
 DEFAULT_PYTHON_VERSION = "3.7"
 CURRENT_DIRECTORY = pathlib.Path(__file__).parent.absolute()
 
-_MINIMAL_ASYNCIO_SUPPORT_PYTHON_VERSION = [3, 6]
+# 'docfx' is excluded since it only needs to run in 'docs-presubmit'
+nox.options.sessions = [
+"unit",
+"unit_grpc_gcp",
+"cover",
+"pytype",
+"lint",
+"lint_setup_py",
+"blacken",
+"docs",
+]
 
 
 def _greater_or_equal_than_36(version_string):

@@ -44,4 +44,49 @@
 """,
 )
 
+# Remove the replacements below once https://.com/googleapis/synthtool/pull/1188 is merged
+
+# Update googleapis/repo-automation-bots repo to main in .kokoro/*.sh files
+s.replace(
+".kokoro/*.sh", "repo-automation-bots/tree/master", "repo-automation-bots/tree/main"
+)
+
+# Customize CONTRIBUTING.rst to replace master with main
+s.replace(
+"CONTRIBUTING.rst",
+"fetch and merge changes from upstream into master",
+"fetch and merge changes from upstream into main",
+)
+
+s.replace(
+"CONTRIBUTING.rst", "git merge upstream/master", "git merge upstream/main",
+)
+
+s.replace(
+"CONTRIBUTING.rst",
+"""export GOOGLE_CLOUD_TESTING_BRANCH=\"master\"""",
+"""export GOOGLE_CLOUD_TESTING_BRANCH=\"main\"""",
+)
+
+s.replace(
+"CONTRIBUTING.rst", r"remote \(``master``\)", "remote (``main``)",
+)
+
+s.replace(
+"CONTRIBUTING.rst", "blob/master/CONTRIBUTING.rst", "blob/main/CONTRIBUTING.rst",
+)
+
+s.replace(
+"CONTRIBUTING.rst", "blob/master/noxfile.py", "blob/main/noxfile.py",
+)
+
+s.replace(
+"docs/conf.py", "master_doc", "root_doc",
+)
+
+s.replace(
+"docs/conf.py", "# The master toctree document.", "# The root toctree document.",
+)
+
+
 s.shell.run(["nox", "-s", "blacken"], hide_output=False)