When a test hands on a real board there is no way on the console to obtain
any information about why it hung.

With sandbox we can actually find out that it died and get a signal or
exit code. Add this to make it easier to figure out what happened.

So instead of:

test/py/u_boot_spawn.py:171: in expect
    c = os.read(self.fd, 1024).decode(errors='replace')
E   OSError: [Errno 5] Input/output error

We get:

test/py/u_boot_spawn.py:171: in expect
    c = os.read(self.fd, 1024).decode(errors='replace')
E   ValueError: U-Boot exited with signal 11 (Signals.SIGSEGV)

Signed-off-by: Simon Glass <sjg@chromium.org>

This produces a lot of code output which is not very helpful and is quite
annoying to wade through. Use the short format by default.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add documentation for this so people can try it out. At present it does
not fully work.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add a second on writing tests, covering when to use Python and C, where
to put the tests, etc. Add a link to the existing Python test
documentation.

Signed-off-by: Simon Glass <sjg@chromium.org>

As Stephen is no longer actively maintaining the uboot-test-hooks
repository, switch to using the instance on our GitLab.

Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Tom Rini <trini@konsulko.com>

Convert test/py/README.md to restructured text and add it to the generated
HTML documentation.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>