add FIXME notice

Dockerfile

@@ -36,6 +36,8 @@ RUN git config --global credential.helper store
 # Fix locales to en_US.UTF-8
 RUN localedef -i en_US -f UTF-8 en_US.UTF-8
 
+# FIXME: due to temporary ipykernel dependency issue, specify ipykernel jupyter
+# version util jupyter fixes this issue.
 RUN pip install --upgrade pip && \
     pip install -U 'protobuf==3.1.0' && \
     pip install -U wheel pillow BeautifulSoup && \