fixes in PyBullet deep_mimic to allow running in pip version

examples/pybullet/gym/pybullet_envs/deep_mimic/learning/solvers/mpi_solver.py

@@ -1,12 +1,12 @@
 from mpi4py import MPI
 import tensorflow as tf
 import numpy as np
-import learning.tf_util as TFUtil
+import pybullet_envs.deep_mimic.learning.tf_util as TFUtil
 import pybullet_utils.math_util as MathUtil
 import pybullet_utils.mpi_util as MPIUtil
 from pybullet_utils.logger import Logger
 
-from learning.solvers.solver import Solver
+from pybullet_envs.deep_mimic.learning.solvers.solver import Solver
 
 class MPISolver(Solver):
     CHECK_SYNC_ITERS = 1000