v2.0.4: fix jupyter issue with permissions on control socket

- Recent addition in jupyter_client caused this bug.  This should be
  removed later, once a newer version of jupyter_core is released.
  The offending code was added to jupyter_client, moved to
  jupyter_core, then fixed in jupyter_core.
- original patch: jupyter/jupyter_client#469  (2019-09-08)
- fix in jupyter_core: jupyter/jupyter_core#177 (2019-11-16)

Makefile

@@ -4,7 +4,7 @@ CRAN_URL=https://cran.microsoft.com/snapshot/2019-12-29/
 # base image - jupyter stuff only, not much software
 VER_BASE=2.0
 # Python
-VER_STD=2.0.3
+VER_STD=2.0.4
 # Julia
 VER_JULIA=2.0.0
 # R

standard.Dockerfile

@@ -138,6 +138,10 @@ RUN pip install --no-cache-dir \
 #           && \
 #    clean-layer.sh
 
+# Fix nbgrader permissions problem
+RUN \
+    sed -i "s@assert '0600' ==.*@assert stat.S_IMODE(os.stat(fname).st_mode) \& 0o77 == 0@" /opt/conda/lib/python3.7/site-packages/jupyter_client/connect.py
+
 ENV CC=clang CXX=clang++