Error message: Upload Failed: A malformed URI was found in the document. Please provide a OpenSettings.RelationshipErrorRewriter to handle these errors while opening a package.
Malformed URI in document
Description:
You'll experience an error message when attempting to run a file through the Cube Updater: "Upload Failed: A malformed URI was found in the document. Please provide a OpenSettings.RelationshipErrorRewriter to handle these errors while opening a package." The updater may have failed because the file contains invalid hyperlinks. This typically occurs with email addresses that have been converted to hyperlinks in Excel.
Solution:
The incompatible hyperlink values should be converted to TEXT in Excel. Save the file and then reupload it into the Cube Updater.
If that doesn't work, read on:
This error may also be referencing a broken or incompatible link that's stored somewhere in your file that aren't email addresses. Best practice is to use as few external links as possible in your files (e.g. a formula referencing another file or multiple files on your local machine). To find your file's links, click the Edit Links button under the Data tab in Excel.
Another potential issue could be the number of EBM connections you have in your file. You should only need ONE for each dataset (e.g. Profitability, Financial, Journal Entry, etc.). If there are duplicates, you can remove them. 
Finally, if you're interested you can read more about code fixes in Excel and on your machine that may allow these files to run anyways: https://github.com/ClosedXML/ClosedXML/issues/249
Solution:
- Remove or fix external links and connections.
- Change linked email addresses to text only.
- Remove redundant EBM connections.
- Try repairing the file via MSOffice.
- Quit Excel and restart your machine.
- Rebuild the file from scratch.