All functions in the API-MS-Win-Core-ErrorHandling-L1-1-0 set are documented exports from KERNEL32:

For most of these functions, the implementations in KERNEL32 version 6.1 and higher are just stubs which transfer the handling to wherever the schema redirects the API Set. The exceptions are:

New Locations

Of the functions that KERNEL32 version 6.1 implements only as stubs, all are exported from KERNELBASE version 6.1 and higher. Moreover, all have non-trivial implementations except:

Schema Redirection

The Windows 7 schema redirects this API Set to KERNEL32, except that when KERNEL32 itself imports from the API Set, the redirection is to KERNELBASE. Thus:

The Windows 8 schema redirects this API Set to KERNELBASE.