d/rules: revert PYTHONPATH mangling, unneeded

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

debian/changelog

@@ -34,8 +34,6 @@ diffoscope (89) unstable; urgency=medium
     + Allow non-text formats to output an empty diff.
   * debian/clean:
     + Remove the egg file when cleaning.
-  * debian/rules:
-    + Fix tests by adding PYTHONPATH.
 
   [ Chris Lamb ]
   * comparators:

debian/rules

@@ -52,7 +52,7 @@ override_dh_auto_test:
 # Let's avoid plonking everything in the "DOS/MBR" category, this is really not
 # a sustainable filetype testing solution (e.g. c051ba9d and c1442405).
 	! grep 'DOS/MBR' -R diffoscope
-	PYTHONPATH="$(CURDIR)" dh_auto_test -O--buildsystem=pybuild
+	dh_auto_test -O--buildsystem=pybuild
 
 override_dh_installman:
 	dh_installman -O--buildsystem=pybuild