title: Getting module 'google.protobuf.descriptor_pool' has no attribute 'Default' in my python script
body: <p>I am new to python and was using a python script written by someone else.  I was running it fine in a different PC. Just had to install coupe of packages including <code>pip3</code>, <code>google-cloud</code>, <code>google-cloud-bigquery</code> and <code>pandas</code>.</p>
  
  <p>Now when I installed the same packages on a different PC, I am unable to run the script.  It is showed the following error first:</p>
  
  <pre><code>module = 'google.protobuf.descriptor_pb2' TypeError: expected bytes, Descriptor found
  </code></pre>
  
  <p>However, when In purged/re-installed/updated packages and also added protobuf3 and protobuf-py3 package, The error has been updated to the following message:  </p>
  
  <pre><code>from google.cloud import bigquery
    File "/home/mobeen/.local/lib/python3.6/site-packages/google/cloud/bigquery/__init__.py", line 35, in &lt;module&gt;
      from google.cloud.bigquery.client import Client
    File "/home/mobeen/.local/lib/python3.6/site-packages/google/cloud/bigquery/client.py", line 50, in &lt;module&gt;
      import google.cloud._helpers
    File "/home/mobeen/.local/lib/python3.6/site-packages/google/cloud/_helpers.py", line 33, in &lt;module&gt;
      from google.protobuf import duration_pb2
    File "/home/mobeen/.local/lib/python3.6/site-packages/google/protobuf/duration_pb2.py", line 8, in &lt;module&gt;
      from google.protobuf import symbol_database as _symbol_database
    File "/home/mobeen/.local/lib/python3.6/site-packages/google/protobuf/symbol_database.py", line 193, in &lt;module&gt;
      _DEFAULT = SymbolDatabase(pool=descriptor_pool.Default())
  AttributeError: module 'google.protobuf.descriptor_pool' has no attribute 'Default'
  </code></pre>
  
  <p>.Any help or leads in this will be appreciated</p>