Done, and this is what happened:
Fetching package metadata .........
Solving package specifications: .
UnsatisfiableError: The following specifications were found to be in conflict:
- navigator-updater -> pyqt >=5.6 -> qt 5.6.*
- pyqt 4* -> qt 4.8.6
- pyqt 4* -> sip 4.16.5
Use "conda info <package>" to see the dependencies for each package.
Is there a way to "uninstall" the newer version of pyqt? If not, what should I do next?