Remove placeholder exit code in unreachable 'black-primer' subprocess handler (#1952)

src/black_primer/lib.py

@@ -58,13 +58,16 @@ async def _gen_check_output(
         await process.wait()
         raise
 
-    if process.returncode != 0:
+    # A non-optional timeout was supplied to asyncio.wait_for, guaranteeing
-        returncode = process.returncode
+    # a timeout or completed process.  A terminated Python process will have a
-        if returncode is None:
+    # non-empty returncode value.
-            returncode = 69
+    assert process.returncode is not None
 
+    if process.returncode != 0:
         cmd_str = " ".join(cmd)
-        raise CalledProcessError(returncode, cmd_str, output=stdout, stderr=stderr)
+        raise CalledProcessError(
+            process.returncode, cmd_str, output=stdout, stderr=stderr
+        )
 
     return (stdout, stderr)