Do a preflight authentication call

[ponyisi]

Resolves #506. Get authentication before actually doing submission, so we can raise an exception early and not hide it in the GuardList in the return value of deliver.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.09%. Comparing base (c58c5aa) to head (6144050).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #520      +/-   ##
==========================================
- Coverage   83.86%   83.09%   -0.78%     
==========================================
  Files          27       27              
  Lines        1599     1674      +75     
==========================================
+ Hits         1341     1391      +50     
- Misses        258      283      +25     

Flag	Coverage Δ
unittests	83.09% <100.00%> (-0.78%)	⬇️

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[ponyisi]

I think the codecov issue is a false positive.

[kyungeonchoi]

Great to have this fix! Thanks!