capture_fd (bool) –
If True, we will also redirect the process file descriptors
1 (stdout), 2 (stderr), and the file descriptors from
sys.stdout.fileno() and sys.stderr.fileno() to the
output. This is useful for capturing output emitted
directly to the process stdout / stderr by external compiled
modules.
Capturing and redirecting the file descriptors can cause loops
in the output stream (where one of the output streams points
to a file descriptor we just captured).
capture_output will attempt to locate
io.IOBase streams in output that point to file
descriptors that we just captured and replace them with
temporary streams that point to (copies of) the original file
descriptor. In addition, capture_output will look
for LogStream objects and will
attempt to locate logging.StreamHandle objects that
would output to a redirected file descriptor and temporarily
redirect those handlers to (copies of) the original file
descriptor.
Note that this process will cover the most common cases, but is
by no means perfect. Use of other output classes or customized
log handlers may still result in output loops (usually
manifesting in an error message about text being left in the
output buffer).