Make ChannelError generic

Instead of using `Any`, which will lose type information if the user
wants to inspect the channel that caused the error, we make it generic.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

src/frequenz/channels/_exceptions.py

@@ -66,7 +66,9 @@
     ```
 """
 
-from typing import Any
+from typing import Generic
+
+from ._generic import ErroredChannelT_co
 
 
 class Error(RuntimeError):
@@ -84,28 +86,28 @@ def __init__(self, message: str):
         super().__init__(message)
 
 
-class ChannelError(Error):
+class ChannelError(Error, Generic[ErroredChannelT_co]):
     """An error that originated in a channel.
 
     All exceptions generated by channels inherit from this exception.
     """
 
-    def __init__(self, message: str, channel: Any):
+    def __init__(self, message: str, channel: ErroredChannelT_co):
         """Initialize this error.
 
         Args:
             message: The error message.
             channel: The channel where the error happened.
         """
         super().__init__(message)
-        self.channel: Any = channel
+        self.channel: ErroredChannelT_co = channel
         """The channel where the error happened."""
 
 
-class ChannelClosedError(ChannelError):
+class ChannelClosedError(ChannelError[ErroredChannelT_co]):
     """A closed channel was used."""
 
-    def __init__(self, channel: Any):
+    def __init__(self, channel: ErroredChannelT_co):
         """Initialize this error.
 
         Args: