Set DEBUG environment variable in Dockerfile and clean up CMD instruction

Dockerfile

@@ -38,6 +38,7 @@ RUN echo "----------------------------------------" && \
     curl -s ifconfig.me && \
     echo "\n----------------------------------------"
 
-CMD ["DEBUG=True", "gunicorn","BridgeMentor.wsgi:application", "--bind", "0.0.0.0:7860", "--timeout", "30", "--workers", "2"]
+ENV DEBUG True
+CMD ["gunicorn","BridgeMentor.wsgi:application", "--bind", "0.0.0.0:7860", "--timeout", "30", "--workers", "2"]
 
 # CMD ["python", "manage.py", "runserver", "7860", "--verbosity", "2","--noreload"]