chore: fix ABC of Formatter and add annotations.

Formatter base class requires .stream, so just force it.

I need to go in and just collapse that ontology, the annotations
are layer violations are painful AF due to the history of how
that evolved and tooling back then being insufficient to do this
sort of refactor safely.  This will be addressed via pkgcore#113.

Signed-off-by: Brian Harring <ferringb@gmail.com>

Author: ferringb

src/snakeoil/cli/tool.py

@@ -17,6 +17,9 @@
 class Tool:
     """Abstraction for commandline tools."""
 
+    out: formatters.Formatter
+    err: formatters.Formatter
+
     def __init__(self, parser, outfile=None, errfile=None):
         """Initialize the utility to run.
 

src/snakeoil/formatters.py

@@ -1,5 +1,6 @@
 """Classes wrapping a file-like object to do fancy output on it."""
 
+import abc
 import errno
 import io
 import locale
@@ -32,7 +33,7 @@ class StreamClosed(KeyboardInterrupt):
 # pylint: disable=C0103
 
 
-class Formatter:
+class Formatter(abc.ABC):
     """Abstract formatter base class.
 
     The types of most of the instance attributes is undefined (depends
@@ -46,10 +47,12 @@ class Formatter:
         (defaults to on).
     """
 
-    def __init__(self):
+    def __init__(self, stream: typing.IO):
         self.autoline = True
         self.wrap = False
+        self.stream = stream
 
+    @abc.abstractmethod
     def write(
         self,
         *args: typing.Union[None, str, typing.Callable[["Formatter"], None]],
@@ -146,7 +149,7 @@ def __init__(
         :param width: maximum line width (defaults to 79).
         :param encoding: encoding unicode strings are converted to.
         """
-        super().__init__()
+        super().__init__(stream)
         # We used to require a TextIOWrapper on py3. We still accept
         # one, guess the encoding from it and grab its underlying
         # bytestream.