ctypes.util.find_library is checking for the presence of the framework
files, which will fail due to macOS Big Sur's "dynamic linker cache".
Since these files really can't be anywhere else, we just hardcode the
path and load them.

See: https://developer.apple.com/documentation/macos-release-notes/macos-big-sur-11-beta-release-notes
(relevent excerpt provided below)

This update takes the approach of leaving the existing behavior as is
for macOS 10.8 (lowest supported version) through 10.15.

Allegedly Apple is going to number Big Sur as macOS 11, although right
now the beta returns a version of "10.16", so this code handles both as
being greater than or equal to "10.16".

| New in macOS Big Sur 11 beta, the system ships with a built-in dynamic
linker cache of all system-provided libraries. As part of this change,
copies of dynamic libraries are no longer present on the filesystem.
Code that attempts to check for dynamic library presence by looking for
a file at a path or enumerating a directory will fail. Instead, check
for library presence by attempting to dlopen() the path, which will
correctly check for the library in the cache. (62986286)

This should never be anything but these paths. Instead of checking for
`os.path.isfile` with `ctypes.util.find_library`, we just try to load
with `ctypes.CDLL` and catch the `OSError` if it fails, add context, and
reraise.