Investigate hypothesis failure

[eivindjahren]

Can be reproduced with @reproduce_failure('6.155.7', b'AXicY3RkcGRgcGLf6MjqKAdiQyAjgyMjGDJ0OMIAI5wJUaJh/4EBDBg1HDInHwAzHRGi2JkAO8kSnA==') on /tests/rd_tests/test_rd_sum.py:241:test_to_from_pandas