fix(deps): fix dependency toward wal-e to avoid issues with Python minimal requirement

db/Dockerfile

@@ -3,7 +3,7 @@ FROM postgres:9.4
 RUN apt-get update \
     && apt-get install -y python-dev lzop pv daemontools curl build-essential \
     && curl --silent --show-error --retry 5 https://bootstrap.pypa.io/get-pip.py | python \
-    && pip install wal-e \
+    && pip install 'wal-e<1.0.0' \
     && apt-get remove -y build-essential python-dev \
     && apt-get autoremove -y \
     && apt-get clean \