Update Dockerfile

Dockerfile

@@ -1,12 +1,6 @@
 FROM ubuntu:16.04
 
-# Set environment variables
-ENV NB_USER=jovyan
-ENV NB_UID=1000
-ENV HOME=/home/${NB_USER}
-ENV JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64/
-
-# Install required system packages and Python 3.6
+# Install Python 3.5 and basic tools
 RUN apt-get update && apt-get install -y \
     software-properties-common \
     wget \
@@ -31,11 +25,13 @@ RUN apt-get update && apt-get install -y \
     && apt-get clean \
     && update-ca-certificates -f
 
-# Upgrade pip for Python 3.6
-RUN python3.5 -m pip install --upgrade pip setuptools
+# Install a pip version compatible with Python 3.5
+RUN python3.5 -m pip install --upgrade "pip<21.0"
 
-# Install Python dependencies
+# Copy requirements file
 COPY requirements.txt /tmp/requirements.txt
+
+# Install Python dependencies
 RUN python3.5 -m pip install --no-cache-dir -r /tmp/requirements.txt
 
 # Create a new user