#284 Correct error message on sentinel discovery of master/slave with password

[popravich]

Rebased from master;

Use more specific error kind.

[codecov]

Codecov Report

Merging #327 into master will increase coverage by <.01%.
The diff coverage is 92.15%.

@@            Coverage Diff             @@
##           master     #327      +/-   ##
==========================================
+ Coverage   96.77%   96.77%   +<.01%     
==========================================
  Files          55       55              
  Lines        7777     7811      +34     
  Branches      621      625       +4     
==========================================
+ Hits         7526     7559      +33     
- Misses        181      183       +2     
+ Partials       70       69       -1

Impacted Files	Coverage Δ
aioredis/errors.py	100% <100%> (ø)	⬆️
tests/sentinel_commands_test.py	100% <100%> (ø)	⬆️
aioredis/sentinel/pool.py	86.21% <100%> (ø)	⬆️
tests/conftest.py	88.38% <66.66%> (-0.72%)	⬇️
tests/sentinel_failover_test.py	87.96% <0%> (+2.25%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9ec600f...abee212. Read the comment docs.

[popravich]

@azinoviev, your thoughts?