Sanitize and modernize pytests

Some of these tests were written before some of our convenient
tooling existed. Additionally, some of the tests were not
cooperating with PEP-8 guidelines or isorted.

This commit does the following:
    - Replaces all calls to make_(user|session) with
      aurweb.db.create(Model, ...).
    - Replace calls to session.add(...) + session.commit() with
      aurweb.db.create.
    - Removes the majority of calls to (session|aurweb.db).delete(...).
    - Replaces session.query calls with aurweb.db.query.
    - Initializes all mutable globals in pytest fixture setup().
    - Makes mutable global declarations more concise:
      `var1, var2 = None, None` -> `var1 = var2 = None`
    - Defines a warning exclusion for test/test_ssh_pub_key.py.
    - Removes the aurweb.testing.models module.
    - Removes some useless pytest.fixture yielding.

As of this commit, developers should use the following guidelines
when writing tests:
    - Always use aurweb.db.(create|delete|query) for database
      operations, where possible.
    - Always define mutable globals in the style: `var1 = var2 = None`.
    - `yield` the most dependent model in pytest setup fixture **iff**
      you must delete records after test runs to maintain database
      integrity. Example: test/test_account_type.py.

This all makes the test code look and behave much cleaner.
Previously, aurweb.testing.setup_test_db was buggy and leaving
objects around in SQLAlchemy's IdentityMap.

Signed-off-by: Kevin Morris <kevr@0cost.org>

test/test_session.py

@@ -4,39 +4,38 @@ from unittest import mock
 
 import pytest
 
+from aurweb.db import create, query
 from aurweb.models.account_type import AccountType
-from aurweb.models.session import generate_unique_sid
+from aurweb.models.session import Session, generate_unique_sid
+from aurweb.models.user import User
 from aurweb.testing import setup_test_db
-from aurweb.testing.models import make_session, make_user
 
-user, _session = None, None
+user = session = None
 
 
 @pytest.fixture(autouse=True)
 def setup():
-    from aurweb.db import session
-
-    global user, _session
+    global user, session
 
     setup_test_db("Users", "Sessions")
 
-    account_type = session.query(AccountType).filter(
-        AccountType.AccountType == "User").first()
-    user = make_user(Username="test", Email="test@example.org",
-                     ResetKey="testReset", Passwd="testPassword",
-                     AccountType=account_type)
-    _session = make_session(UsersID=user.ID, SessionID="testSession",
-                            LastUpdateTS=datetime.utcnow())
+    account_type = query(AccountType,
+                         AccountType.AccountType == "User").first()
+    user = create(User, Username="test", Email="test@example.org",
+                  ResetKey="testReset", Passwd="testPassword",
+                  AccountType=account_type)
+    session = create(Session, UsersID=user.ID, SessionID="testSession",
+                     LastUpdateTS=datetime.utcnow())
 
 
 def test_session():
-    assert _session.SessionID == "testSession"
-    assert _session.UsersID == user.ID
+    assert session.SessionID == "testSession"
+    assert session.UsersID == user.ID
 
 
 def test_session_user_association():
     # Make sure that the Session user attribute is correct.
-    assert _session.User == user
+    assert session.User == user
 
 
 def test_generate_unique_sid():