python3-pint: fix ptests

1. Add missing ptest dependency (pytest-subtest)

2. The testsuite is installed in both the site-packages and ${PTEST_PATH}
folders, however some dependencies are only available in the site-packages
folder, so many test cases fail.
At this point of the branch lifecycle I decided not to refactor the recipe, but
rather to just use the installation in the site-packages dir to run the
tests (switch to that folder in the run-ptest script)

3. Fix the run-ptest script to output PASS/FAIL status.

Signed-off-by: Gyorgy Sarvari <skandigraun@gmail.com>

meta-python/recipes-devtools/python/python3-pint_0.19.1.bb

@@ -27,9 +27,5 @@ RDEPENDS:${PN} += " \
 
 RDEPENDS:${PN}-ptest += " \
 	${PYTHON_PN}-pytest \
+        ${PYTHON_PN}-pytest-subtests \
 "
-
-do_install_ptest() {
-	install -d ${D}${PTEST_PATH}/testsuite
-	cp -rf ${S}/pint/testsuite/* ${D}${PTEST_PATH}/testsuite/
-}