add missing libmariadb3 package, update gunicorn package hash, resolves #113

Dockerfile

@@ -60,7 +60,7 @@ RUN set -x && \
   apt-get update && \
   # Install required distro packages
   apt-get -y install nginx-light && \
-  apt-get -y --no-install-recommends install python3 python3-setuptools python3-pip python3-dev gcc make default-libmysqlclient-dev && \
+  apt-get -y --no-install-recommends install python3 python3-setuptools python3-pip python3-dev gcc make default-libmysqlclient-dev libmariadb3 && \
   # Install pipenv
   pip3 --disable-pip-version-check install pipenv && \
   # Create a 'app' user which the application will run as

Pipfile.lock

@@ -91,6 +91,7 @@
         },
         "gunicorn": {
             "hashes": [
+                "sha256:9dcc4547dbb1cb284accfb15ab5667a0e5d1881cc443e0677b4882a4067a807e",
                 "sha256:e0a968b5ba15f8a328fdfd7ab1fcb5af4470c28aaf7e55df02a99bc13138e6e8"
             ],
             "index": "pypi",