Troubleshooting

Run brew update twice.
Run brew doctor and fix all the warnings (outdated Xcode/CLT and unbrewed dylibs are very likely to cause problems).
Check that Command Line Tools for Xcode (CLT) and Xcode are up to date.
If commands fail with permissions errors, check the permissions of /usr/local’s subdirectories. If you’re unsure what to do, you can run:
```
$ cd /usr/local 
$ sudo chown -R $(whoami) bin etc include lib sbin share var opt Cellar Caskroom Frameworks
```

QGIS 3 Specific Problems

The maximum number of open file descriptors

Since the build of QGIS 3 has a lot of dependencies you perhaps could run into an error related to the lack of resources allocated to the shell. Luckily you can change that using the command ulimit. Check if ulimit -n is bigger than 1024 and it it’s not set it ulimit -n 1024 . It’s up to you if you want to reset to you previous limit after you build or install QGIS.

Post-install could not finish

It seems that there was a small change in OTB, I will correct it in the next release of QGIS. You can solve this by temporarily renaming OtbUtils file.

$ mv /usr/local/Cellar/qgis/3.6.0_4/QGIS.app/Contents/Resources/python/plugins/otb/OTBUtils.py /usr/local/Cellar/qgis/3.6.0_4/QGIS.app/Contents/Resources/python/plugins/otb/OtbUtils.py

Fixing dependencies

Sometimes errors installing or building are related to incorrect installed or linked dependencies. We recommend you to do the following and try to build or install again:

Remove the cache

$ rm -rf $(brew --cache)

and the temporary files in /tmp related to the build if any.

A failed installation perhaps has build qgis_customwidgets.py you need to delete it.

$ rm /usr/local/lib/python3.7/site-packages/PyQt5/uic/widget-plugins/qgis_customwidgets.py

Reinstall a relink some dependencies:

$ brew reinstall ninja gsl python qt sip-qt5 pyqt-qt5 pyqt5-webkit qscintilla2-qt5 six bison flex pkg-config
$ brew link --overwrite pyqt-qt5
$ brew unlink gettext python && brew link --force gettext python