build(python): exit with success status if no samples found

.kokoro/docker/docs/fetch_gpg_keys.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+# Copyright 2020 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.
+
+# A script to fetch gpg keys with retry.
+# Avoid jinja parsing the file.
+# 
+
+function retry {
+    if [[ "${#}" -le 1 ]]; then
+	echo "Usage: ${0} retry_count commands.."
+	exit 1
+    fi
+    local retries=${1}
+    local command="${@:2}"
+    until [[ "${retries}" -le 0 ]]; do
+	$command && return 0
+	if [[ $? -ne 0 ]]; then
+	    echo "command failed, retrying"
+	    ((retries--))
+	fi
+    done
+    return 1
+}
+
+# 3.6.9, 3.7.5 (Ned Deily)
+retry 3 gpg --keyserver ha.pool.sks-keyservers.net --recv-keys \
+      0D96DF4D4110E5C43FBFB17F2D347EA6AA65421D
+
+# 3.8.0 (Łukasz Langa)
+retry 3 gpg --keyserver ha.pool.sks-keyservers.net --recv-keys \
+      E3FF2839C048B25C084DEBE9B26995E310250568
+
+#