Fix Ftrace explorer, python -> python3

Change-Id: Iafe4578192da946ee55b900d1ad3ae8f5cc35377
diff --git a/src/traced/probes/ftrace/test/explorer.html b/src/traced/probes/ftrace/test/explorer.html
index a474df5..d100264 100755
--- a/src/traced/probes/ftrace/test/explorer.html
+++ b/src/traced/probes/ftrace/test/explorer.html
@@ -15,8 +15,8 @@
 # limitations under the License.
 
 cd $(dirname $0)
-python -m webbrowser -t "http://localhost:8000/$(basename $0)"
-python -m SimpleHTTPServer
+python3 -m webbrowser -t "http://localhost:8000/$(basename $0)"
+python3 -m http.server
 
 <<-EOF
 -->