Ensure that BinaryFileInput is an IOBase

- Rename the open handle property to an `open()` method, to ensure that
  it has an `open()` method -- though not part of the target interface,
  this is a common expectation around handling binary streams

- Use ABC `register()` to make sure that the class passes isinstance()
  checks even though it does not subclass/inherit

Author: sirosen

src/check_jsonschema/file_wrapper.py

@@ -13,6 +13,7 @@
 - `close()` does nothing on stdin
 """
 
+import io
 import os
 import stat
 import sys
@@ -43,11 +44,10 @@ def check_can_open(self) -> None:
             # Open and close the file in case we're opening it for
             # reading so that we can catch at least some errors in
             # some cases early.
-            self._open_handle.close()
-            self._stream = None
+            self.open()
+            self.close()
 
-    @property
-    def _open_handle(self) -> t.BinaryIO:
+    def open(self) -> t.BinaryIO:
         if self._stream is None:
             self._stream = open(self.name, "rb")
         return self._stream
@@ -60,7 +60,7 @@ def close(self) -> None:
             self._stream = None
 
     def __getattr__(self, name: str) -> t.Any:
-        return getattr(self._open_handle, name)
+        return getattr(self.open(), name)
 
     def __repr__(self) -> str:
         return "BinaryFileInput(filename={self.filename!r})"
@@ -77,4 +77,8 @@ def __exit__(
         self.close()
 
     def __iter__(self) -> t.Iterator[bytes]:
-        return iter(self._open_handle)
+        return iter(self.open())
+
+
+# register as an IOBase implementation, since pyjson5 relies on an isinstance() check
+io.IOBase.register(BinaryFileInput)