Log warning if errors are occured during the execute method

[YariKartoshe4ka]

Если во время вызова метода execute произошли ошибки, они будут записаны в логе с уровнем WARNING
Исправляет #42

[codecov]

Codecov Report

Merging #127 (4134e93) into master (6d094b5) will decrease coverage by 4.15%.
The diff coverage is 28.57%.

@@            Coverage Diff             @@
##           master     #127      +/-   ##
==========================================
- Coverage   78.65%   74.50%   -4.16%     
==========================================
  Files          11       11              
  Lines         342      353      +11     
==========================================
- Hits          269      263       -6     
- Misses         73       90      +17     

Impacted Files	Coverage Δ
tests/test_api.py	43.75% <22.22%> (-56.25%)	⬇️
src/vk/session.py	56.64% <25.00%> (-1.84%)	⬇️
src/vk/exceptions.py	97.43% <100.00%> (+0.06%)	⬆️
tests/test_exceptions.py	77.77% <0.00%> (-22.23%)	⬇️
tests/conftest.py	90.00% <0.00%> (ø)

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