No module named google.protobuf.internal

(venv)[jalal@ivcgpu1 CNN_age_gender]$ python age_gender_example.py
Traceback (most recent call last):
  File "age_gender_example.py", line 17, in <module>
    import caffe
  File "/home/grad3/jalal/caffe/python/caffe/__init__.py", line 1, in <module>
    from .pycaffe import Net, SGDSolver, NesterovSolver, AdaGradSolver, RMSPropSolver, AdaDeltaSolver, AdamSolver, NCCL, Timer
  File "/home/grad3/jalal/caffe/python/caffe/pycaffe.py", line 15, in <module>
    import caffe.io
  File "/home/grad3/jalal/caffe/python/caffe/io.py", line 8, in <module>
    from caffe.proto import caffe_pb2
  File "/home/grad3/jalal/caffe/python/caffe/proto/caffe_pb2.py", line 4, in <module>
    from google.protobuf.internal import enum_type_wrapper
ImportError: No module named google.protobuf.internal
(venv)[jalal@ivcgpu1 CNN_age_gender]$ pip uninstall protobuf
Cannot uninstall requirement protobuf, not installed
Storing complete log in /home/grad3/jalal/.pip/pip.log
(venv)[jalal@ivcgpu1 CNN_age_gender]$ cat /home/grad3/jalal/.pip/pip.log
------------------------------------------------------------
/home/grad3/jalal/venv/bin/pip run on Mon Sep 25 00:39:13 2017
Cannot uninstall requirement protobuf, not installed

Exception information:
Traceback (most recent call last):
  File "/home/grad3/jalal/venv/lib/python2.7/site-packages/pip/basecommand.py", line 134, in main
    status = self.run(options, args)
  File "/home/grad3/jalal/venv/lib/python2.7/site-packages/pip/commands/uninstall.py", line 54, in run
    requirement_set.uninstall(auto_confirm=options.yes)
  File "/home/grad3/jalal/venv/lib/python2.7/site-packages/pip/req.py", line 940, in uninstall
    req.uninstall(auto_confirm=auto_confirm)
  File "/home/grad3/jalal/venv/lib/python2.7/site-packages/pip/req.py", line 440, in uninstall
    raise UninstallationError("Cannot uninstall requirement %s, not installed" % (self.name,))
UninstallationError: Cannot uninstall requirement protobuf, not installed
(venv)[jalal@ivcgpu1 CNN_age_gender]$