I was recently troubleshooting an installation of Plone and tried to install one of the hundreds of Plone products. Immediately after restarting Zope, four ominous words (and a long trace) appeared on the screen: No traversable adapter found. After an hour-or-two of troubleshooting, I found out how to solve the problem.

As it turns out, this tends to happen (assuming the error appeared after installing a few Products into Zope/Plone) because either:

  1. one of the installed Products is corrupted, or
  2. one or more dependencies for the products is missing.

To fix this, we first have to uninstall all the add-on Products one-by-one until we isolate the one that is causing Zope/Plone to show that error message. Keeping the error-causing plugin installed, we can then stop Zope, then restart it in foreground mode by typing the following commands (remember to replace /path/to/zope/instance with the real path to your Zope instance):

sudo /path/to/zope/instance/bin/zopectl stop
sudo /path/to/zope/instance/bin/zopectl fg

Note: the above commands are for Ubuntu/Debian/Debian-derivative Linux systems. They will require some modifications to work on other systems.

After Zope starts up by using the above commands, keep the terminal window open and browse to your Zope/Plone installation in a web browser. When the page comes up (and the “No traversable adapter found” error is displayed), look at the terminal screen. A traceback should have been displayed. Near the bottom of the screen, there should be a specific error. The error at the bottom of the might screen start with:

ImportError:

If this is the case, you should search for the dependency that the error refers to in Google, download it, and install it. For example, the product that I was trying to install required the DataGridField and AddRemoveWidget Products. I was able to download those from http://www.plone.org/products. After installing the dependencies, Zope/Plone worked perfectly.

However, if you receive a different error, there are a few main solutions that you could try:

  1. Try re-downloading the Product after clearing your browser’s cache. Internet Explorer is known to download files incorrectly and corrupt them from time-to-time.
  2. Try downloading a different version of the Product. There is a slight chance that the particular version of the Product that you were trying to install had a bug. If this is the case, make sure to report the bug so that it can be fixed by the author.
  3. Check to see if the Product that you are using is compatible with the version of Plone that you are using. Many plugins that are designed for Plone 2 will not work on Plone 3 without some modification. There may, however, be a pre-release version of the Product that does work for your version of Plone.

Hopefully, these tips will help you! If you have any thoughts on this subject, feel free to comment below!

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