pin msgpack (pydata#3793)

* pin msgpack

* fix package name

Author: dcherian

ci/requirements/py36-min-all-deps.yml

@@ -26,6 +26,7 @@ dependencies:
   - isort
   - lxml=4.4  # Optional dep of pydap
   - matplotlib=3.1
+  - msgpack-python=0.6  # remove once distributed is bumped. distributed GH3491
   - mypy=0.761  # Must match .pre-commit-config.yaml
   - nc-time-axis=1.2
   - netcdf4=1.4

ci/requirements/py36-min-nep18.yml

@@ -8,6 +8,7 @@ dependencies:
   - coveralls
   - dask=2.4
   - distributed=2.4
+  - msgpack-python=0.6  # remove once distributed is bumped. distributed GH3491
   - numpy=1.17
   - pandas=0.25
   - pint=0.9  # Actually not enough as it doesn't implement __array_function__yet!