We currently pin netCDF4 to version 1.5. However, I think netCDF4 does not really follow semantic versioning, e.g. python 2 support was dropped in version 1.5.6. So they may actually be doing something like 1.major.minor[.patch] - I asked about their versioning scheme in Unidata/netcdf4-python#1090.

So I wonder if we would need to pin netCDF to version to version 1.5.4.