Add PyLint as a development dependency

Use `pylint calsocial` to run the static analysis.

calsocial/__init__.py

@@ -32,8 +32,6 @@ def get_locale():
     Selects the best locale based on values sent by the browser.
     """
 
-    from flask import request
-
     supported_languages = ['en', 'hu']
 
     if 'l' in request.args and request.args['l'].lower() in supported_languages:
@@ -62,7 +60,7 @@ def route(*args, **kwargs):
     ``**kwargs`` will be passed verbatim to `Flask.route()`.
     """
 
-    def decorator(func):
+    def decorator(func):  # pylint: disable=missing-docstring
         setattr(func, 'routing', (args, kwargs))
 
         return func
@@ -176,7 +174,8 @@ class CalendarSocialApp(Flask):
         form = RegistrationForm()
 
         if form.validate_on_submit():
-            # TODO: This might become False later, if we want registrations to be confirmed via E-mail
+            # TODO: This might become False later, if we want registrations to be confirmed via
+            #       e-mail
             user = User(active=True)
 
             form.populate_obj(user)

calsocial/calendar_system/gregorian.py

@@ -30,10 +30,10 @@ def to_timestamp(func):
     """
 
     @wraps(func)
-    def decorator(*args, **kwargs):
+    def _decorator(*args, **kwargs):
         return func(*args, **kwargs).timestamp()
 
-    return decorator
+    return _decorator
 
 
 class GregorianCalendar(CalendarSystem):

calsocial/forms.py

@@ -55,6 +55,8 @@ class TimezoneField(SelectField):
     """
 
     def __init__(self, *args, **kwargs):
+        self.data = None
+
         kwargs.update({
             'choices': [
                 (pytz.timezone(tz), tz.replace('_', ' '))

calsocial/models.py

@@ -74,6 +74,7 @@ class User(db.Model, UserMixin):
     """
 
     __tablename__ = 'users'
+    # pylint: disable=invalid-name
     id = db.Column(db.Integer(), primary_key=True)
 
     #: The username of the user.  This is also the display name and thus is immutable
@@ -132,11 +133,12 @@ class User(db.Model, UserMixin):
         return f'<User {self.id}({self.username})>'
 
 
-class Role(db.Model, RoleMixin):
+class Role(db.Model, RoleMixin):  # pylint: disable=too-few-public-methods
     """Database model for roles
     """
 
     __tablename__ = 'roles'
+    # pylint: disable=invalid-name
     id = db.Column(db.Integer(), primary_key=True)
 
     #: The name of the role
@@ -175,6 +177,7 @@ class Event(db.Model):
     """
 
     __tablename__ = 'events'
+    # pylint: disable=invalid-name
     id = db.Column(db.Integer(), primary_key=True)
 
     #: The ID of the user who created the event