'user_dylan' is found in SLS 'base:core.shell' and SLS 'base:web.sites'

The application of the these states fails with the following error:

web01:
    Data failed to compile:
----------
    Detected conflicting IDs, SLS IDs need to be globally unique.
    The conflicting ID is 'user_dylan' and is found in SLS 'base:core.shell' and SLS 'base:web.sites'

This is because a new state, user_dylan has been added to the core states. This duplicate needs to be renamed or removed.