py/persistentcode: Always close reader even if an exception is raised.

Fixes issue #3874.

Signed-off-by: Damien George <damien@micropython.org>

tests/extmod/vfs_userfs.py

@@ -69,6 +69,7 @@ user_files = {
     "/usermod1.py": b"print('in usermod1')\nimport usermod2",
     "/usermod2.py": b"print('in usermod2')",
     "/usermod3.py": b"syntax error",
+    "/usermod4.mpy": b"syntax error",
 }
 os.mount(UserFS(user_files), "/userfs")
 
@@ -86,6 +87,12 @@ try:
 except SyntaxError:
     print("SyntaxError in usermod3")
 
+# import a .mpy file with a syntax error (file should be closed on error)
+try:
+    import usermod4
+except ValueError:
+    print("ValueError in usermod4")
+
 # unmount and undo path addition
 os.umount("/userfs")
 sys.path.pop()

tests/extmod/vfs_userfs.py.exp

@@ -15,3 +15,9 @@ stat /usermod3.py
 open /usermod3.py rb
 ioctl 4 0
 SyntaxError in usermod3
+stat /usermod4
+stat /usermod4.py
+stat /usermod4.mpy
+open /usermod4.mpy rb
+ioctl 4 0
+ValueError in usermod4