core: Fix issues with reloading folder modules

Closes sopel-irc#899, obviates and closes sopel-irc#932.

sopel/bot.py

@@ -165,14 +165,19 @@ def setup(self):
             stderr("Warning: Couldn't load any modules")
 
     def unregister(self, obj):
+        if not callable(obj):
+            return
         if hasattr(obj, 'rule'):  # commands and intents have it added
             for rule in obj.rule:
-                self._callables[obj.priority][rule].remove(obj)
+                callb_list = self._callables[obj.priority][rule]
+                if obj in callb_list:
+                    callb_list.remove(obj)
         if hasattr(obj, 'interval'):
             # TODO this should somehow find the right job to remove, rather than
             # clearing the entire queue. Issue #831
             self.scheduler.clear_jobs()
-        if getattr(obj, '__name__', None) == 'shutdown':
+        if (getattr(obj, '__name__', None) == 'shutdown'
+                and obj in self.shutdown_methods):
             self.shutdown_methods.remove(obj)
 
     def register(self, callables, jobs, shutdowns):

sopel/loader.py

@@ -11,6 +11,9 @@
 if sys.version_info.major >= 3:
     basestring = (str, bytes)
 
+# Can be implementation-dependent
+_regex_type = type(re.compile(''))
+
 
 def get_module_description(path):
     good_file = (os.path.isfile(path) and path.endswith('.py')
@@ -108,6 +111,10 @@ def enumerate_modules(config, show_all=False):
 
 
 def compile_rule(nick, pattern):
+    # Not sure why this happens on reloads, but it shouldn't cause problems…
+    if isinstance(pattern, _regex_type):
+        return pattern
+
     pattern = pattern.replace('$nickname', nick)
     pattern = pattern.replace('$nick', r'{}[,:]\s+'.format(nick))
     flags = re.IGNORECASE