Ignore the DeprecationWarning regarding the `imp` module deprecation, as it...

Ignore the DeprecationWarning regarding the `imp` module deprecation, as it comes from a 3rd party library

Signed-off-by: Mattia Rizzolo <mattia@debian.org>

pytest.ini

 [pytest]
 junit_family=xunit2
+# this comes from binwalk
+# https://github.com/ReFirmLabs/binwalk/issues/507
+filterwarnings =
+    ignore:the imp module is deprecated in favour of importlib.*:DeprecationWarning