http://buildbot.python.org/all/#/builders/80/builds/244

       (Link target) -> 
         python3_d.def : error LNK2001: unresolved external symbol PyImport_GetModule [D:\buildarea\3.x.ware-win81-release.refleak\build\PCbuild\python3dll.vcxproj]
         python3_d.def : error LNK2001: unresolved external symbol Py_UTF8Mode [D:\buildarea\3.x.ware-win81-release.refleak\build\PCbuild\python3dll.vcxproj]
         D:\buildarea\3.x.ware-win81-release.refleak\build\PCbuild\amd64\python3_d.lib : fatal error LNK1120: 2 unresolved externals [D:\buildarea\3.x.ware-win81-release.refleak\build\PCbuild\python3dll.vcxproj]

Maybe it's related to this recent change:

commit 4e29f566e8821c09d8274eadcdd355e8b1284b8b
Author: Serhiy Storchaka <storchaka@gmail.com>
Date:   Tue May 22 20:59:42 2018 +0300

    Add missed details of the C API introduced in 3.7. (GH-7047)
    
    * Set the limited API version for PyImport_GetModule and PyOS_*Fork
      functions.
    * Add PyImport_GetModule and Py_UTF8Mode in PC/python3.def.
    * Add several functions in Doc/data/refcounts.dat.

The two missing symbols are defined by:

#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03070000
PyAPI_FUNC(PyObject *) PyImport_GetModule(PyObject *name);
#endif

and

#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03070000
PyAPI_DATA(int) Py_UTF8Mode;
#endif

They are not part of the stable ABI.