Nothing has changed recently in the PEP 538 implementation itself, and both those builders were green last month:

* https://buildbot.python.org/all/#/builders/60/builds/181
* https://buildbot.python.org/all/#/builders/79/builds/185

The first failing debug build was https://buildbot.python.org/all/#/builders/60/builds/182 which rearranged some parts of the startup sequence: https://github.com/python/cpython/commit/d19d8d5279f156bc8f6736b5f16f069879b9519b

Similarly, the 3.7 builds started failing in https://buildbot.python.org/all/#/builders/124/builds/489, which made Py_Initialize work more closely to the way it worked in Python 3.6: https://github.com/python/cpython/commit/0c90d6f75931da4fec84d06c2efe9dd94bb96b77

So given the output reported in the current build failures, my guess would be that something has gotten out of sequence in the code that has to handle re-encoding and decoding command line values and environment variables that have initially been decoded incorrectly (i.e. as surrogate escaped ASCII).