diff --git a/aprendizations/learnapp.py b/aprendizations/learnapp.py
index 5f012ce..6295640 100644
--- a/aprendizations/learnapp.py
+++ b/aprendizations/learnapp.py
@@ -10,8 +10,7 @@ from typing import Dict
 
 # third party libraries
 import bcrypt
-from sqlalchemy import create_engine, func
-from sqlalchemy.orm import sessionmaker
+import sqlalchemy as sa
 import networkx as nx
 
 # this project
@@ -29,7 +28,7 @@ class LearnException(Exception):
     pass
 
 
-class DatabaseUnusableException(LearnException):
+class DatabaseUnusableError(LearnException):
     pass
 
 
@@ -48,7 +47,7 @@ class LearnApp(object):
             yield session
             session.commit()
         except Exception:
-            logger.error('DB rollback!!!')
+            logger.error('!!! Database rollback !!!')
             session.rollback()
             raise
         finally:
@@ -268,12 +267,12 @@ class LearnApp(object):
                             f'database')
 
     # ------------------------------------------------------------------------
-    # setup and check database
+    # setup and check database contents
     # ------------------------------------------------------------------------
     def db_setup(self, db):
         logger.info(f'Checking database "{db}":')
-        engine = create_engine(f'sqlite:///{db}', echo=False)
-        self.Session = sessionmaker(bind=engine)
+        engine = sa.create_engine(f'sqlite:///{db}', echo=False)
+        self.Session = sa.orm.sessionmaker(bind=engine)
         try:
             with self.db_session() as s:
                 n = s.query(Student).count()
@@ -281,7 +280,7 @@ class LearnApp(object):
                 q = s.query(Answer).count()
         except Exception:
             logger.error(f'Database "{db}" not usable!')
-            raise DatabaseUnusableException()
+            raise DatabaseUnusableError()
         else:
             logger.info(f'{n:6} students')
             logger.info(f'{m:6} topics')
@@ -311,7 +310,7 @@ class LearnApp(object):
 
         # iterate over topics and populate graph
         topics = config.get('topics', {})
-        g = self.deps                   # the dependency graph
+        g = self.deps       # dependency graph
 
         g.add_nodes_from(topics.keys())
         for tref, attr in topics.items():
@@ -442,10 +441,10 @@ class LearnApp(object):
             total_topics = s.query(Topic).count()
 
             # answer performance
-            totalans = dict(s.query(Answer.student_id, func.count(Answer.ref)).
+            totalans = dict(s.query(Answer.student_id, sa.func.count(Answer.ref)).
                             group_by(Answer.student_id).
                             all())
-            rightans = dict(s.query(Answer.student_id, func.count(Answer.ref)).
+            rightans = dict(s.query(Answer.student_id, sa.func.count(Answer.ref)).
                             filter(Answer.grade == 1.0).
                             group_by(Answer.student_id).
                             all())
diff --git a/aprendizations/main.py b/aprendizations/main.py
index 5a415c2..a2ee135 100644
--- a/aprendizations/main.py
+++ b/aprendizations/main.py
@@ -12,7 +12,7 @@ import sys
 import tornado
 
 # this project
-from .learnapp import LearnApp, DatabaseUnusableException
+from .learnapp import LearnApp, DatabaseUnusableError
 from .serve import WebApplication
 from .tools import load_yaml
 from . import APP_NAME, APP_VERSION
@@ -149,7 +149,7 @@ def main():
     try:
         learnapp = LearnApp(arg.conffile, prefix=arg.prefix, db=arg.db,
                             check=arg.check)
-    except DatabaseUnusableException:
+    except DatabaseUnusableError:
         logging.critical('Failed to start application.')
         print('--------------------------------------------------------------')
         print('Could not find a usable database. Use one of the follwing     ')
--
libgit2 0.21.2