use 3.6 alpine as base image

Dockerfile

@@ -1,4 +1,29 @@
-FROM python:3.6
+# Copyright 2016-2019 The Van Valen Lab at the California Institute of
+# Technology (Caltech), with support from the Paul Allen Family Foundation,
+# Google, & National Institutes of Health (NIH) under Grant U24CA224309-01.
+# All rights reserved.
+#
+# Licensed under a modified 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.github.com/vanvalenlab/kiosk-bucket-monitor/LICENSE
+#
+# The Work provided may be used for non-commercial academic purposes only.
+# For any other use of the Work, including commercial use, please contact:
+# vanvalenlab@gmail.com
+#
+# Neither the name of Caltech nor the names of its contributors may be used
+# to endorse or promote products derived from this software without specific
+# prior written permission.
+#
+# 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.
+# ============================================================================
+FROM python:3.6-alpine
 
 WORKDIR /usr/src/app
 
@@ -8,4 +33,4 @@ RUN pip install -r requirements.txt
 
 COPY . .
 
-CMD ["python", "monitor-bucket.py"]
+CMD ["/bin/sh", "-c", "python", "monitor-bucket.py"]