Don't forget to copy the MANIFEST.in :trollface:
@@ -10,7 +10,7 @@ RUN apt-get update && \
# copy powerfulseal package
WORKDIR /powerfulseal
-COPY Makefile LICENSE README.md setup.py /powerfulseal/
+COPY Makefile LICENSE README.md setup.py MANIFEST.in /powerfulseal/
COPY powerfulseal/ /powerfulseal/powerfulseal/
# install it with pip
