Read rsync output while it runs

Read the output as it arrives, split on newlines and carriage returns,
instead of all at once with communicate(). This is needed for the
progress bar. Invalid UTF-8 in the output is replaced instead of raising.

tests/test_remote.py

@@ -257,6 +257,8 @@ class RecordPopen:
 
     def __init__(self, args: list[str], **kwargs: Any) -> None:
         RecordPopen.calls.append(args)
+        self.stdin = io.BytesIO()
+        self.stdout = io.BytesIO(b'sent 1 bytes  received 2 bytes\ntotal size is 3\n')
 
     def __enter__(self) -> 'RecordPopen':
         return self
@@ -264,8 +266,8 @@ class RecordPopen:
     def __exit__(self, *args: Any) -> None:
         pass
 
-    def communicate(self) -> tuple[bytes, None]:
-        return b'sent 1 bytes  received 2 bytes\ntotal size is 3\n', None
+    def wait(self) -> int:
+        return RecordPopen.returncode
 
 
 @pytest.mark.usefixtures('connect')