Taken from: https://github.com/ceph/ceph/pull/44112

--- a/src/mgr/CMakeLists.txt
+++ b/src/mgr/CMakeLists.txt
@@ -34,6 +34,7 @@
     mgr_commands.cc
     $<TARGET_OBJECTS:mgr_cap_obj>)
   add_executable(ceph-mgr ${mgr_srcs})
+  target_compile_definitions(ceph-mgr PRIVATE PY_SSIZE_T_CLEAN)
   target_link_libraries(ceph-mgr
     osdc client heap_profiler
     global-static ceph-common