This new Dockerfile is working

Dockerfile

@@ -1,20 +1,12 @@
-FROM ubuntu
+# Keep this Python image version manually maintained
+FROM python:3.7-stretch
 
-RUN DEBIAN_FRONTEND=noninteractive && \
-    apt -y update && \
-    apt install -y build-essential \
-        python3 python3-dev python3-pip python3-venv git ca-certificates && \
-    adduser --disabled-password --force-badname SmokeDetector \
-        --gecos SmokeDetector && \
-    su - SmokeDetector sh -c '\
-        git clone https://github.com/Charcoal-SE/SmokeDetector.git && \
+RUN adduser --disabled-password --force-badname smokey --gecos smokey && \
+    su --login smokey sh -c '\
+        git clone --depth=50 https://github.com/Charcoal-SE/SmokeDetector.git && \
         cd SmokeDetector && \
-        python3 -m venv venv && \
-        . ./venv/bin/activate && \
-        pip3 install -r user_requirements.txt --upgrade' && \
-    pip3 install -r ~SmokeDetector/SmokeDetector/requirements.txt --upgrade && \
-    apt autoremove -y --purge build-essential python3-dev && \
-    apt clean && \
+        pip3 install --user -r user_requirements.txt --upgrade' && \
+    pip3 install -r ~smokey/SmokeDetector/requirements.txt --upgrade && \
     rm -rf /root/* /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
-CMD ["su", "-", "SmokeDetector"]
+CMD ["su", "--login", "smokey", "-c", "/home/smokey/SmokeDetector/docker-startup.sh"]