Exclude python scripts from RPM shebang check

The newest Fedora packaging rules print warnings for scripts using the
/usr/bin/python shebang:

    *** WARNING: mangling shebang in /usr/bin/arc_summary.py from
    #!/usr/bin/python to #!/usr/bin/python2. This will become an ERROR,
    fix it manually!

Fedora wants all cross compatible scripts to pick python3.  Since we
don't want our users to have to pick a specific version of python, we
exclude our scripts from the RPM build check.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Giuseppe Di Natale <[email protected]>
Signed-off-by: Tony Hutter <[email protected]>
Closes openzfs#7360 
Closes openzfs#7399

rpm/generic/zfs.spec.in

@@ -36,6 +36,16 @@
 %bcond_with    debug
 %bcond_with    systemd
 
+# Python permits the !/usr/bin/python shebang for scripts that are cross
+# compatible between python2 and python3, but Fedora 28 does not.  Fedora
+# wants us to choose python3 for cross-compatible scripts.  Since we want
+# to support python2 and python3 users, exclude our scripts from Fedora 28's
+# RPM build check, so that we don't get a bunch of build warnings.
+#
+# Details: https://github.com/zfsonlinux/zfs/issues/7360
+#
+%global __brp_mangle_shebangs_exclude_from arc_summary.py|arcstat.py|dbufstat.py|test-runner.py
+
 # Generic enable switch for systemd
 %if %{with systemd}
 %define _systemd 1