Added custom ArgumentErrors for bucket and folder nonexistence
Merge branch 'bug_fixes' of github.com:griddynamics/Behavior-Analytic-Starter-Kit into bug_fixes

# By schinilov
# Via schinilov
* 'bug_fixes' of github.com:griddynamics/Behavior-Analytic-Starter-Kit:
  Update Qubell-setup-guide.md