One of the projects that I am contributing to as part of my research is hosted on SourceForge. I found a bug, fixed it, and created a patch. Everything was ready to commit to the Subversion repository.
git svn dcommit --username=caseyrobinson Committing to https://protomol.svn.sourceforge.net/svnroot/protomol ... Authentication realm: <https://protomol.svn.sourceforge.net:443> SourceForge Subversion area Password for 'caseyrobinson': Authorization failed: MKACTIVITY of '/svnroot/protomol/!svn/act/9e685c30-a6bd-43d6-9541-d1351ef14e3c': authorization failed: Could not authenticate to server: rejected Basic challenge (https://protomol.svn.sourceforge.net) at /usr/libexec/git-core/git-svn line 4891
When I saw this error I became quite confused and frustrated. I checked my password. That wasn't it. My project privileges were correct as well. I asked the other contributors which led to numerous possibilities and hours of testing. All were plausible suggestions, however none worked out.
It turns out that my password was using characters, single and double quotes, that satisfied the website but SVN doesn't accept. There is even a support ticket from 17 months ago where it is apparent that this issue is known. SourceForge should at least update their registration form to warn that certain characters will cause problems with some services.