Revert "setuptools --install-layout argument is no longer supported..."

This is creating trouble during tests. Scripts are being installed to
usr/local/bin instead of usr/bin and that is tripping up the dh_usrlocal
helper.

This reverts commit f8c8b15.

stdeb/util.py

@@ -1680,7 +1680,7 @@ def build_dsc(debinfo,
 
 RULES_OVERRIDE_INSTALL_TARGET_PY2 = "        %(python2_binname)s setup.py install --force --root=debian/%(package)s --no-compile -O0 --install-layout=deb %(install_prefix)s %(no_python2_scripts_cli_args)s"  # noqa: E501
 
-RULES_OVERRIDE_INSTALL_TARGET_PY3 = "        python3 setup.py install --force --root=debian/%(package3)s --no-compile -O0 %(install_prefix)s %(no_python3_scripts_cli_args)s"  # noqa: E501
+RULES_OVERRIDE_INSTALL_TARGET_PY3 = "        python3 setup.py install --force --root=debian/%(package3)s --no-compile -O0 --install-layout=deb %(install_prefix)s %(no_python3_scripts_cli_args)s"  # noqa: E501
 
 RULES_OVERRIDE_INSTALL_TARGET = """
 override_dh_auto_install: