perf scripts python: Add Python 3 support to SchedGui.py

Fix a single syntax error in SchedGui.py to support both Python 2 and
Python 3. This should have no functional change.

Signed-off-by: Jeremy Cline <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Herton Krzesinski <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/scripts/python/Perf-Trace-Util/lib/Perf/Trace/SchedGui.py

···
 try:
 	import wx
 except ImportError:
-	raise ImportError, "You need to install the wxpython lib for this script"
+	raise ImportError("You need to install the wxpython lib for this script")
 
 
 class RootFrame(wx.Frame):