Change: bump python version to 3.7

Dockerfile

-FROM python:3.5.7-slim-buster
+FROM python:3.7-slim-buster
 
 RUN mkdir /app
 ADD . /app

bin/_venv

@@ -8,7 +8,7 @@ echo "OK"
 
 if [ ! -f .venv/bin/activate ]; then
   echo "Creating new venv in: ./.venv"
-  virtualenv ./.venv
+  python3 -m venv ./.venv
 fi
 
 echo "Loading virtualenv: ./.venv"

bin/install.sh

 #!/usr/bin/env bash
 
-source ./_venv
+source ./bin/_venv
 
 echo "Installing dependencies..."
 pip3 install -r requirements.txt --no-cache-dir