add initial pylint config, just one checker

will clean these up one by one so we can use fail-under=10 for
buildbot pylint

.pylintrc

@@ -0,0 +1,5 @@
+# -*- mode: conf; -*-
+
+[MESSAGES CONTROL]
+disable=all
+enable=dangerous-default-value

src/wuttjamaican/conf.py

@@ -61,10 +61,12 @@ class WuttaConfig:
     * one or more INI files
     * "defaults" provided by app logic
 
-    :param files: List of file paths from which to read config values.
+    :param files: Optional list of file paths from which to read
+       config values.
 
-    :param defaults: Initial values to use as defaults.  This gets
+    :param defaults: Optional dict of initial values to use as
-       converted to :attr:`defaults` during construction.
+       defaults.  This gets converted to :attr:`defaults` during
+       construction.
 
     :param appname: Value to assign for :attr:`appname`.
 
@@ -187,8 +189,8 @@ class WuttaConfig:
 
     def __init__(
             self,
-            files=[],
+            files=None,
-            defaults={},
+            defaults=None,
             appname='wutta',
             usedb=None,
             preferdb=None,
@@ -199,11 +201,11 @@ class WuttaConfig:
 
         # read all files requested
         self.files_read = []
-        for path in files:
+        for path in files or []:
             self._load_ini_configs(path, configs, require=True)
 
         # add config for use w/ setdefault()
-        self.defaults = configuration.Configuration(defaults)
+        self.defaults = configuration.Configuration(defaults or {})
         configs.append(self.defaults)
 
         # master config set

src/wuttjamaican/email.py

@@ -370,7 +370,7 @@ class EmailHandler(GenericHandler):
         """
         return Message(**kwargs)
 
-    def make_auto_message(self, key, context={}, default_subject=None, **kwargs):
+    def make_auto_message(self, key, context=None, default_subject=None, **kwargs):
         """
         Make a new email message using config to determine its
         properties, and auto-generating body from a template.
@@ -407,6 +407,7 @@ class EmailHandler(GenericHandler):
         * :meth:`get_auto_txt_body()`
         * :meth:`get_auto_html_body()`
         """
+        context = context or {}
         kwargs['key'] = key
         if 'sender' not in kwargs:
             kwargs['sender'] = self.get_auto_sender(key)
@@ -452,7 +453,7 @@ class EmailHandler(GenericHandler):
         # fall back to global default, if present
         return self.config.get(f'{self.config.appname}.email.default.replyto')
 
-    def get_auto_subject(self, key, context={}, rendered=True, setting=None, default=None):
+    def get_auto_subject(self, key, context=None, rendered=True, setting=None, default=None):
         """
         Returns automatic :attr:`~wuttjamaican.email.Message.subject`
         line for a message, as determined by config.
@@ -481,6 +482,7 @@ class EmailHandler(GenericHandler):
         if not rendered:
             return template
 
+        context = context or {}
         return Template(template).render(**context)
 
     def get_auto_subject_template(self, key, setting=None, default=None):
@@ -561,7 +563,7 @@ class EmailHandler(GenericHandler):
         return self.config.get_list(f'{self.config.appname}.email.default.{typ}',
                                     default=[])
 
-    def get_auto_txt_body(self, key, context={}):
+    def get_auto_txt_body(self, key, context=None):
         """
         Returns automatic :attr:`~wuttjamaican.email.Message.txt_body`
         content for a message, as determined by config.  This renders
@@ -569,9 +571,10 @@ class EmailHandler(GenericHandler):
         """
         template = self.get_auto_body_template(key, 'txt')
         if template:
+            context = context or {}
             return template.render(**context)
 
-    def get_auto_html_body(self, key, context={}):
+    def get_auto_html_body(self, key, context=None):
         """
         Returns automatic
         :attr:`~wuttjamaican.email.Message.html_body` content for a
@@ -580,6 +583,7 @@ class EmailHandler(GenericHandler):
         """
         template = self.get_auto_body_template(key, 'html')
         if template:
+            context = context or {}
             return template.render(**context)
 
     def get_auto_body_template(self, key, mode):
@@ -740,7 +744,7 @@ class EmailHandler(GenericHandler):
         return self.config.get_bool(f'{self.config.appname}.mail.send_emails',
                                     default=False)
 
-    def send_email(self, key=None, context={}, message=None, sender=None, recips=None, **kwargs):
+    def send_email(self, key=None, context=None, message=None, sender=None, recips=None, **kwargs):
         """
         Send an email message.
 
@@ -810,7 +814,7 @@ class EmailHandler(GenericHandler):
             # auto-create message from key + context
             if sender:
                 kwargs['sender'] = sender
-            message = self.make_auto_message(key, context, **kwargs)
+            message = self.make_auto_message(key, context or {}, **kwargs)
             if not (message.txt_body or message.html_body):
                 raise RuntimeError(f"message (type: {key}) has no body - "
                                    "perhaps template file not found?")

tox.ini

@@ -10,6 +10,12 @@ commands = pytest {posargs}
 [testenv:nox]
 extras = tests
 
+[testenv:pylint]
+basepython = python3.11
+extras =
+deps = pylint
+commands = pylint wuttjamaican
+
 [testenv:coverage]
 basepython = python3.11
 extras = db,tests