update Dockerfile

Dockerfile

@@ -1,12 +1,7 @@
 FROM ubuntu
 ENV TZ=Etc/UTC
 RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
-RUN apt-get update && apt-get install --yes python3 pip pkg-config libsystemd-dev
-
-RUN update-alternatives --install /usr/bin/python python /usr/bin/python3.7
-
-# Set python3.7 as the default python
-RUN update-alternatives --set python /usr/bin/python3.7
+RUN apt-get update && apt-get install --yes python3.7.15 pip pkg-config libsystemd-dev
 
 # Set the working directory in the container to /app
 WORKDIR /app