BUG #18408: ERROR: could not load library

The following bug has been logged on the website:

Bug reference: 18408
Logged by: Ben Watson
Email address: ben(dot)watson(at)maroonanalytics(dot)com
PostgreSQL version: 16.2
Operating system: Win11
Description:

I have been trying to get PostgreSQL 16.2, compiled by Visual C++ build
1937, 64-bit running on a win11 machine. I am having a number of issues, but
one that looks very much like a bug

CREATE EXTENSION plpython3u;

Throws this error. ERROR: could not load library "C:/Program
Files/PostgreSQL/16/lib/plpython3.dll": The specified module could not be
found.

But the file clearly exists in that directory.

But the because it is a windows machine the path should really be
"C:\Program Files\PostgreSQL\16\lib\plpython3.dll". Looks like some unix
style file paths are in use.

Is this a bug? or just misleading output. In any case that command does not
work in my environment.

PS running the sql shell as admin or not admin makes no difference.