On removing the workaround we introduced in iris-grib#208, the original signature problem as reported in #30, seems to have reappeared.

Context:

• running under Linux, via Travis
• The error is seen here in the Travis testing log : https://travis-ci.org/github/SciTools/iris-grib/jobs/731255839#L1237
• The testcode that triggers this is in this test
• The versions of all packages installed can be seen from the "conda list" command in the Travis log
  • ( N.B. open the collapsed section to view installed packages )