title: caffe import error: even after installing it successfully, on ubuntu 18.04
body: <p>I'm getting caffe import error even after installing it successfully using the command <code>sudo apt install caffe-cpu</code>. I was able to find caffe file at <code>/usr/lib/python3/dist-packages/caffe</code> (Path was added to PYTHONPATH). All requirements mentioned in the requirements.txt file of caffe directory was also installed.</p>
  
  <p>I'm using Ubuntu 18.04 LTS, Python3.</p>
  
  <p>Could anyone help me with this error?</p>
  
  <pre><code>import caffe        
  
  Traceback (most recent call last):
        File "6_reconstruct_alphabet_image.py", line 17, in &lt;module&gt;
          import caffe
        File "/usr/lib/python3/dist-packages/caffe/__init__.py", line 1, in &lt;module&gt;
          from .pycaffe import Net, SGDSolver, NesterovSolver, AdaGradSolver, RMSPropSolver, AdaDeltaSolver, AdamSolver, NCCL, Timer
        File "/usr/lib/python3/dist-packages/caffe/pycaffe.py", line 15, in &lt;module&gt;
          import caffe.io
        File "/usr/lib/python3/dist-packages/caffe/io.py", line 2, in &lt;module&gt;
          import skimage.io
        File "/usr/lib/python3/dist-packages/skimage/__init__.py", line 158, in &lt;module&gt;
          from .util.dtype import *
        File "/usr/lib/python3/dist-packages/skimage/util/__init__.py", line 7, in &lt;module&gt;
          from .arraycrop import crop
        File "/usr/lib/python3/dist-packages/skimage/util/arraycrop.py", line 8, in &lt;module&gt;
          from numpy.lib.arraypad import _validate_lengths
      ImportError: cannot import name '_validate_lengths'
  </code></pre>