fix settings.py for pymysql

[koxudaxi]

This PR fix settings.py for using pymysql.

Related issues

#50

[codecov]

Codecov Report

Merging #51 into master will not change coverage by %.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master       #51   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           12        12           
  Lines          539       539           
  Branches        67        67           
=========================================
  Hits           539       539           

Impacted Files	Coverage Δ
local_data_api/settings.py	100.00% <ø> (ø)

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