Pin pip to version 20.2 to avoid bug in 20.3

Author: jakekara

lts-app/backend.Dockerfile

@@ -4,7 +4,9 @@ COPY let-them-speak /lts-app
 
 WORKDIR /lts-app
 
-RUN pip install -U pip && pip install -r requirements.txt
+# Pinning pip 20.2 until this issue is fixed https://github.com/pypa/pip/issues/9180 
+#RUN pip install -U pip && pip install -r requirements.txt
+RUN pip install --upgrade pip~=20.2.0 && pip install -r requirements.txt
 
 EXPOSE 7082