[Utils] Tools for marking things unsafe for general use (#2326)

* Tools for marking things unsafe for general use

* I'm facepalming so much...

Actually, make the two do something different 
instead of getting distracted writing different docs for both based on intended usage.

* local scopes mmkay + tests

* Move file to adress feedback

* typo fix

* Update __init__.py

* Fix issue with exported names in __init__

* changelog

redbot/core/utils/safety.py

@@ -0,0 +1,49 @@
+import warnings
+import functools
+
+
+def unsafe(f, message=None):
+    """
+    Decorator form for marking a function as unsafe.
+
+    This form may not get used much, but there are a few cases
+    we may want to add something unsafe generally, but safe in specific uses.
+
+    The warning can be supressed in the safe context with warnings.catch_warnings
+    This should be used sparingly at most.
+    """
+
+    def wrapper(func):
+        @functools.wraps(func)
+        def get_wrapped(*args, **kwargs):
+            actual_message = message or f"{func.__name__} is unsafe for use"
+            warnings.warn(actual_message, stacklevel=3, category=RuntimeWarning)
+            return func(*args, **kwargs)
+
+        return get_wrapped
+
+    return wrapper
+
+
+def warn_unsafe(f, message=None):
+    """
+    Function to mark function from dependencies as unsafe for use.
+
+    Warning: There is no check that a function has already been modified.
+    This form should only be used in init, if you want to mark an internal function
+    as unsafe, use the decorator form above.
+
+    The warning can be suppressed in safe contexts with warnings.catch_warnings
+    This should be used sparingly at most.
+    """
+
+    def wrapper(func):
+        @functools.wraps(func)
+        def get_wrapped(*args, **kwargs):
+            actual_message = message or f"{func.__name__} is unsafe for use"
+            warnings.warn(actual_message, stacklevel=3, category=RuntimeWarning)
+            return func(*args, **kwargs)
+
+        return get_wrapped
+
+    return wrapper(f)