chore(py_library): add some excludes in docs/conf.py

This should fix build failures in python-bigquery.
Example:
googleapis/python-bigquery#205

* also add a comment

Source-Author: Takashi Matsuo <tmatsuo@google.com>
Source-Date: Mon Aug 3 15:08:00 2020 -0700
Source-Repo: googleapis/synthtool
Source-Sha: 4f8f5dc24af79694887385015294e4dbb214c352
Source-Link: googleapis/synthtool@4f8f5dc

docs/conf.py

@@ -21,6 +21,7 @@
 sys.path.insert(0, os.path.abspath(".."))
 
 # For plugins that can not read conf.py.
+# See also: https://github.com/docascode/sphinx-docfx-yaml/issues/85
 sys.path.insert(0, os.path.abspath("."))
 
 __version__ = ""
@@ -93,7 +94,12 @@
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
-exclude_patterns = ["_build"]
+exclude_patterns = [
+    "_build",
+    "samples/AUTHORING_GUIDE.md",
+    "samples/CONTRIBUTING.md",
+    "samples/snippets/README.rst",
+]
 
 # The reST default role (used for this markup: `text`) to use for all
 # documents.

synth.metadata

@@ -4,22 +4,83 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/python-org-policy.git",
-        "sha": "c5fbce5f0f05aa425c6c9fafc8263757da876c3c"
+        "sha": "b98739cfbe6356b55a85acec932cb7c4ff7e8846"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "bfcdbe0da977b2de6c1c0471bb6dc2f1e13bf669"
+        "sha": "4f8f5dc24af79694887385015294e4dbb214c352"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "bfcdbe0da977b2de6c1c0471bb6dc2f1e13bf669"
+        "sha": "4f8f5dc24af79694887385015294e4dbb214c352"
       }
     }
+  ],
+  "generatedFiles": [
+    ".flake8",
+    ".github/CONTRIBUTING.md",
+    ".github/ISSUE_TEMPLATE/bug_report.md",
+    ".github/ISSUE_TEMPLATE/feature_request.md",
+    ".github/ISSUE_TEMPLATE/support_request.md",
+    ".github/PULL_REQUEST_TEMPLATE.md",
+    ".github/release-please.yml",
+    ".kokoro/build.sh",
+    ".kokoro/continuous/common.cfg",
+    ".kokoro/continuous/continuous.cfg",
+    ".kokoro/docker/docs/Dockerfile",
+    ".kokoro/docker/docs/fetch_gpg_keys.sh",
+    ".kokoro/docs/common.cfg",
+    ".kokoro/docs/docs-presubmit.cfg",
+    ".kokoro/docs/docs.cfg",
+    ".kokoro/presubmit/common.cfg",
+    ".kokoro/presubmit/presubmit.cfg",
+    ".kokoro/publish-docs.sh",
+    ".kokoro/release.sh",
+    ".kokoro/release/common.cfg",
+    ".kokoro/release/release.cfg",
+    ".kokoro/samples/lint/common.cfg",
+    ".kokoro/samples/lint/continuous.cfg",
+    ".kokoro/samples/lint/periodic.cfg",
+    ".kokoro/samples/lint/presubmit.cfg",
+    ".kokoro/samples/python3.6/common.cfg",
+    ".kokoro/samples/python3.6/continuous.cfg",
+    ".kokoro/samples/python3.6/periodic.cfg",
+    ".kokoro/samples/python3.6/presubmit.cfg",
+    ".kokoro/samples/python3.7/common.cfg",
+    ".kokoro/samples/python3.7/continuous.cfg",
+    ".kokoro/samples/python3.7/periodic.cfg",
+    ".kokoro/samples/python3.7/presubmit.cfg",
+    ".kokoro/samples/python3.8/common.cfg",
+    ".kokoro/samples/python3.8/continuous.cfg",
+    ".kokoro/samples/python3.8/periodic.cfg",
+    ".kokoro/samples/python3.8/presubmit.cfg",
+    ".kokoro/test-samples.sh",
+    ".kokoro/trampoline.sh",
+    ".kokoro/trampoline_v2.sh",
+    ".trampolinerc",
+    "CODE_OF_CONDUCT.md",
+    "CONTRIBUTING.rst",
+    "LICENSE",
+    "MANIFEST.in",
+    "docs/_static/custom.css",
+    "docs/_templates/layout.html",
+    "docs/conf.py",
+    "docs/multiprocessing.rst",
+    "renovate.json",
+    "scripts/decrypt-secrets.sh",
+    "scripts/readme-gen/readme_gen.py",
+    "scripts/readme-gen/templates/README.tmpl.rst",
+    "scripts/readme-gen/templates/auth.tmpl.rst",
+    "scripts/readme-gen/templates/auth_api_key.tmpl.rst",
+    "scripts/readme-gen/templates/install_deps.tmpl.rst",
+    "scripts/readme-gen/templates/install_portaudio.tmpl.rst",
+    "setup.cfg",
+    "testing/.gitignore"
   ]
 }