unable to add unset environment variables via <checkbox-snap>.configure

[Kristin Chuang]

[Steps]
On any system with checkbox-snappy installed:
1. Check what environment variables are currently set:
     $ sudo checkbox-snappy.configure -l
2. Try setting a not-yet-set variable, e.g. "TEST_SNAP":
     $ sudo checkbox-snappy.configure TEST_SNAP=foo
3. Check if the changes in step 2 is saved:
     $ sudo checkbox-snappy.configure -l
4. Launch the actual configuration file to see if the changes made in step 2 is saved:
     $ cat /writable/system-data/var/snap/checkbox-<project-name>/current/checkbox.conf

[Expected]
Changes in step 2 are reflected in both step 3 and 4

[Actual]
Changes in step 2 are not reflected in either step 3 or 4

[Workaround]
The only way to workaround/solve this problem is to write the new settings directly into the checkbox.conf configuration file

[Kristin Chuang (kristinchuang)]

Two possible solutions I'm seeing:

1. Add the feature of allowing checkbox-snappy.configure to add unset variables

2. List all variables that could be used inside checkbox.conf from the very beginning.