fixes #92: since django-3.0 sqlmigrate (and migrate) does not work

[shimizukawa]

Feature or Bugfix

• Bugfix

Purpose

• fix manage.py sqlmigrate

Detail

• Django-3.0 changed the implementation of the postgres backend, causing sqlmigrate to stop working.
• https://github.com/django/django/pull/11594/files#diff-e3fea5d09fbc3286aafc3ed3ea77299b7649528754f410afa725045a8d2f74afR165-R184

Relates

• _create_index_sql() doesn't accept a keyword argument 'name' #92

[codecov]

Codecov Report

Merging #93 (d1f9652) into master (a67bb59) will increase coverage by 0.43%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master      #93      +/-   ##
==========================================
+ Coverage   47.01%   47.45%   +0.43%     
==========================================
  Files           3        3              
  Lines         251      255       +4     
  Branches       68       68              
==========================================
+ Hits          118      121       +3     
- Misses        123      124       +1     
  Partials       10       10              

Impacted Files	Coverage Δ
django_redshift_backend/base.py	43.93% <66.66%> (+0.52%)	⬆️

---

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 a67bb59...d1f9652. Read the comment docs.