r = r"(s*('[^']+',s*)('[^']+',s*)('[^']+')s*)"
sub = r'{"key1": 1"key2": 2"key3": 3}'

json = "[%s]" % re.sub(r, sub, text)

[{"key1": 'str10', "key2": 'str20', "key3": 'str30'}, {"key1": 'str11', "key2": 'str21', "key3": 'str31'}, {"key1": 'str11', "key2": 'str21', "key3": 'str31'}]