add flake8

Pipfile

@@ -4,15 +4,16 @@ verify_ssl = true
 name = "pypi"
 
 [packages]
-flask = "*"
-python-dotenv = "*"
-flask-migrate = "*"
-flask-sqlalchemy = "*"
-sqlalchemy = "*"
-waitress = "*"
-pyyaml = "*"
+flask = "~=2.0.1"
+python-dotenv = "~=0.17.1"
+flask-migrate = "~=3.0.1"
+flask-sqlalchemy  = "~=2.5.1"
+sqlalchemy = "~=1.4.18"
+waitress = "~=2.0.0"
+pyyaml = "~=5.4.1"
 
 [dev-packages]
+flake8 = "~=3.9.2"
 
 [requires]
 python_version = "3.8"