Trying to update to 1.6.10 package fails

Often I get the message that I can update the board package. When I try that, I get the error that the file cannot be downloaded. The URL that is used is http://downloads.sodaq.net/sodaqsamdboards-1.6.10.tar.bz2

However http://downloads.sodaq.net/test/sodaqsamdboards-1.6.10.tar.bz2 does work but the IDE doesn’t use that URL, it uses the other one.

In the IDE under File->Preferences->Additional Board Manager URLs you can either use the standard URL:

http://downloads.sodaq.net/package_sodaq_index.json

or the test URL:

http://downloads.sodaq.net/test/package_sodaq_index.json

The standard URL contains the official releases (currently on v1.6.9) and the test URL will also include unofficial releases which may be subject to further changes. Currently, there is a v1.6.10 test version.

Unless you need to use some feature that has not made the latest official release, I would recommend sticking with the standard URL. Because the test releases are subject to change, this can confuse the board manager and how it caches the files. If you see a CRC mismatch error, this can usually be fixed by clearing the board manager cache directory.

On a PC this directory is located in:
/Users//AppData/Local/Arduino15/staging