Resolving Compatibility Issue between python2 and python3 (#1)

* fixed map function of python2 to list(map) in feedback position error code
* add absolute_import for the compatibility of python2,3

---------

Co-authored-by: s-kim <s-kim@jsk.imi.i.u-tokyo.ac.jp>

src/joint_trajectory_action/joint_trajectory_action.py

@@ -28,14 +28,16 @@
 """
 Baxter RSDK Joint Trajectory Action Server
 """
+from __future__ import absolute_import
+
 import bisect
 from copy import deepcopy
 import math
 import operator
 import numpy as np
 
-import bezier
-import minjerk
+from . import bezier
+from . import minjerk
 
 import rospy
 
@@ -58,6 +60,11 @@
 import baxter_interface
 
 
+# Python2's xrange equals Python3's range, and xrange is removed on Python3
+if not hasattr(__builtins__, 'xrange'):
+    xrange = range
+
+
 class JointTrajectoryActionServer(object):
     def __init__(self, limb, reconfig_server, rate=100.0,
                  mode='position_w_id', interpolation='bezier'):
@@ -203,10 +210,11 @@ def _update_feedback(self, cmd_point, jnt_names, cur_time):
         self._fdbk.desired.time_from_start = rospy.Duration.from_sec(cur_time)
         self._fdbk.actual.positions = self._get_current_position(jnt_names)
         self._fdbk.actual.time_from_start = rospy.Duration.from_sec(cur_time)
-        self._fdbk.error.positions = map(operator.sub,
-                                         self._fdbk.desired.positions,
-                                         self._fdbk.actual.positions
-                                        )
+        self._fdbk.error.positions = list(map(operator.sub,
+                                              self._fdbk.desired.positions,
+                                              self._fdbk.actual.positions
+                                             )
+                                         )
         self._fdbk.error.time_from_start = rospy.Duration.from_sec(cur_time)
         self._server.publish_feedback(self._fdbk)