Log message:
py-pyobjc: updated to 6.2.1

Version 6.2.1
* Ensure package ‘pyobjc’ won’t try to build the PubSub bindings on macOS 10.15
* Minor tweaks to build and pass tests on macOS 10.14 with the latest Xcode that \ 
can be installed on that version of macOS.
* Fix SystemError in block edge case
* PyObjC raised a SystemError when converting a callable into an ObjC block when \ 
the callable is a bound method without positional arguments.
* Fix crash on catalina caused by writing to read-only memory.
* Make sure the SDK detection works when the version is not in the SDK name
* There were no SDK updates in Xcode 11.5 and Xcode 11.6 (beta)