po2json errors on possibly duplicated ids even when verbose format is used

If I understand correctly, this warning 
```
Duplicate msgid ("Something: ${ employee.name }" and "Something: ${ employeesStr }" in the same context will be interpreted as the same key...
```
is relevant only if `ttag po2json --format=compact`

If verbose format is used, there should probably be no warning, or at least execution should proceed?