feat: support older version of python

[pkyosx]

No description provided.

[github-actions]

Coverage after merging feat/porting_3_6 into master

98.69%

Coverage Report

File	Branches	Funcs	Lines	Uncovered Lines
believe
__init__.py	100%	100%	100%
dict_matcher.py	100%	100%	100%
error.py	100%	100%	100%
internal.py	100%	100%	97.62%	49
list_matcher.py	100%	100%	96.23%	30, 36
number_matcher.py	100%	100%	100%
other_matcher.py	100%	100%	100%
str_matcher.py	100%	100%	98.11%	55–56

[github-actions]

Unit Test Results

  1 files  ±0    1 suites  ±0   0s ⏱️ ±0s
20 tests ±0  20 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit f6a6d59. ± Comparison against base commit 8a92aa4.

♻️ This comment has been updated with latest results.