Fix Python 3.7 incompatibility.

I also added flake8 and pylint to the dev requirements.

.flake8

@@ -4,4 +4,6 @@ ignore =
   E221,
   # multi spaces before op - I line up assignments often
   E401,
-  # multiple imports on one line
+  # multiple imports on one line
+  E722,
+  # ignore bare except in tests

requirements-dev.txt

@@ -4,3 +4,9 @@
 
 setuptools ~= 67.7
 pytest ~= 7.3
+
+# I'm going to try leaving the versions off since we're supporting drastically different Python
+# versions.  I want the most up to date I can get in each, at least until one of them makes a
+# backwards incompatible change.
+flake8
+pylint

tests/mysql_test.py

@@ -455,7 +455,7 @@ def test_emoticons_as_literal(cursor):
     assert result == v
 
 
-@lru_cache
+@lru_cache()
 def _generate_str(length, encoding=None):
     """
     Returns either a string or bytes, depending on whether encoding is provided,