Update Dockerfile

Dockerfile

@@ -12,6 +12,7 @@ RUN apt-get update && \
     apt-get install -y gcc && \
     pip install --no-cache-dir --upgrade pip && \
     pip install --no-cache-dir -r requirements.txt && \
+    pip install --no-cache-dir pyflakes &&\
     apt-get remove -y gcc && \
     apt-get autoremove -y && \
     rm -rf /var/lib/apt/lists/*