title: conda update anaconda Fails | ClobberError
body: <p>I am trying to update all conda packages.</p>
  <p>Tried running these command</p>
  <blockquote>
  <p>conda update anaconda</p>
  <p>conda update --all</p>
  </blockquote>
  <p>But getting this error after confirming on most of the packages.</p>
  <p>How to solve and update all the packages ?</p>
  <pre><code>ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/__pycache__/wait.cpython-36.pyc'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  
  
  ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/connection.py'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  
  
  ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/request.py'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  
  
  ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/response.py'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  
  
  ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/retry.py'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  
  
  ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/selectors.py'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  
  
  ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/ssl_.py'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  
  
  ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/timeout.py'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  
  
  ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/url.py'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  
  
  ClobberError: The package 'defaults::pip-10.0.1-py36_0' cannot be installed due to a
  path collision for 'lib/python3.6/site-packages/pip/_vendor/urllib3/util/wait.py'.
  This path already exists in the target prefix, and it won't be removed
  by an uninstall action in this transaction. The path is one that conda
  doesn't recognize. It may have been created by another package manager.
  </code></pre>