error.sh

$ docker build -t gcr.io/foo/polls .                    
Sending build context to Docker daemon   1.12MB
Step 1/7 : FROM gcr.io/google_appengine/python
latest: Pulling from google_appengine/python
1d47b358304c: Pull complete 
c6cf9be4ad08: Pull complete 
3c2cba919283: Pull complete 
b5267a7c948d: Pull complete 
327bc3d676fa: Pull complete 
7084178c9da9: Pull complete 
31fbffa5723c: Pull complete 
98a0ff8d38f3: Pull complete 
093b2756f844: Pull complete 
ceb73bc4cc66: Pull complete 
1e5c1be07413: Pull complete 
2af8e37f2e04: Pull complete 
Digest: sha256:73f43d9b52e95c821dcd2d6e1bc42ebb1b002623263cea5ae517e6f81d56bc37
Status: Downloaded newer image for gcr.io/google_appengine/python:latest
 ---> b6b482fb5994
Step 2/7 : RUN virtualenv /env
 ---> Running in 35644c5abdfc
New python executable in /env/bin/python
Installing setuptools, pip, wheel...done.
Removing intermediate container 35644c5abdfc
 ---> 01d30aa357f6
Step 3/7 : ENV PATH /env/bin:$PATH
 ---> Running in b2d82fbf571b
Removing intermediate container b2d82fbf571b
 ---> 80c2caa53893
Step 4/7 : ADD requirements.txt /app/requirements.txt
 ---> c79b8390111a
Step 5/7 : RUN /env/bin/pip install -r /app/requirements.txt
 ---> Running in b01aa456bd35
Collecting Django==2.0.3 (from -r /app/requirements.txt (line 1))
  Could not find a version that satisfies the requirement Django==2.0.3 (from -r /app/requirements.txt (line 1)) (from versions: 1.1.3, 1.1.4, 1.2, 1.2.1, 1.2.2, 1.2.3, 1.2.4, 1.2.5, 1.2.6, 1.2.7, 1.3, 1.3.1, 1.3.2, 1.3.3, 1.3.4, 1.3.5, 1.3.6, 1.3.7, 1.4, 1.4.1, 1.4.2, 1.4.3, 1.4.4, 1.4.5, 1.4.6, 1.4.7, 1.4.8, 1.4.9, 1.4.10, 1.4.11, 1.4.12, 1.4.13, 1.4.14, 1.4.15, 1.4.16, 1.4.17, 1.4.18, 1.4.19, 1.4.20, 1.4.21, 1.4.22, 1.5, 1.5.1, 1.5.2, 1.5.3, 1.5.4, 1.5.5, 1.5.6, 1.5.7, 1.5.8, 1.5.9, 1.5.10, 1.5.11, 1.5.12, 1.6, 1.6.1, 1.6.2, 1.6.3, 1.6.4, 1.6.5, 1.6.6, 1.6.7, 1.6.8, 1.6.9, 1.6.10, 1.6.11, 1.7, 1.7.1, 1.7.2, 1.7.3, 1.7.4, 1.7.5, 1.7.6, 1.7.7, 1.7.8, 1.7.9, 1.7.10, 1.7.11, 1.8a1, 1.8b1, 1.8b2, 1.8rc1, 1.8, 1.8.1, 1.8.2, 1.8.3, 1.8.4, 1.8.5, 1.8.6, 1.8.7, 1.8.8, 1.8.9, 1.8.10, 1.8.11, 1.8.12, 1.8.13, 1.8.14, 1.8.15, 1.8.16, 1.8.17, 1.8.18, 1.8.19, 1.9a1, 1.9b1, 1.9rc1, 1.9rc2, 1.9, 1.9.1, 1.9.2, 1.9.3, 1.9.4, 1.9.5, 1.9.6, 1.9.7, 1.9.8, 1.9.9, 1.9.10, 1.9.11, 1.9.12, 1.9.13, 1.10a1, 1.10b1, 1.10rc1, 1.10, 1.10.1, 1.10.2, 1.10.3, 1.10.4, 1.10.5, 1.10.6, 1.10.7, 1.10.8, 1.11a1, 1.11b1, 1.11rc1, 1.11, 1.11.1, 1.11.2, 1.11.3, 1.11.4, 1.11.5, 1.11.6, 1.11.7, 1.11.8, 1.11.9, 1.11.10, 1.11.11, 1.11.12, 1.11.13)
No matching distribution found for Django==2.0.3 (from -r /app/requirements.txt (line 1))
The command '/bin/sh -c /env/bin/pip install -r /app/requirements.txt' returned a non-zero code: 1

fix is to use python3 in docker image definition, PR GoogleCloudPlatform/python-docs-samples#1533