bpy.ops.object.mode_set(mode='POSE')
for bone in bones:
    x = bone.location[0] + random.uniform(-0.2, 0.2)
    y = bone.location[1] + random.uniform(-0.2, 0.2)
    z = bone.location[2] + random.uniform(-0.2, 0.2)
    bone.location[0] = x
    bone.location[1] = y
    bone.location[2] = z
    bpy.context.scene.update()
bpy.context.scene.render.filepath = outfile_name
bpy.ops.render.render(write_still=True)

import bpy
import random

armature = bpy.context.scene.objects['Armature']

for pose_bone in armature.pose.bones:
    x = pose_bone.location[0] + random.uniform(-0.2, 0.2)
    y = pose_bone.location[1] + random.uniform(-0.2, 0.2)
    z = pose_bone.location[2] + random.uniform(-0.2, 0.2)
    pose_bone.location[0] = x
    pose_bone.location[1] = y
    pose_bone.location[2] = z