tools.compile_rule: better whitespace handling for $nick placeholder

If the placeholder is followed by a space, replace it with a pattern
that will consume extra whitespace but doesn't require any.

If the placeholder is NOT followed by a space, use the original pattern
that requires at least one space to match.

Author: dgw

sopel/tools/__init__.py

@@ -214,9 +214,10 @@ def compile_rule(nick, pattern, alias_nicks):
         nick = re.escape(nick)
 
     pattern = pattern.replace('$nickname', nick)
-    pattern = pattern.replace('$nick', r'{}[,:]\s+'.format(nick))
+    pattern = pattern.replace('$nick ', r'{}[,:]\s*'.format(nick))  # @rule('$nick hi')
+    pattern = pattern.replace('$nick', r'{}[,:]\s+'.format(nick))  # @rule('$nickhi')
     flags = re.IGNORECASE
-    if '\n' in pattern:
+    if '\n' in pattern:  # TODO: Why do we have this? IRC lines can't contain \n
         flags |= re.VERBOSE
     return re.compile(pattern, flags)