FIX: Fixed mistake in 7a525917.

tests/test_file.py

@@ -52,6 +52,7 @@ def setup():
     upload_file.write("hello world\n")
     upload_file.close()
     os.mkdir("testfolder")
+    os.mkdir("testfolder/subfolder")
     with open("testfolder/test1.dat", "w") as upload_file:
         upload_file.write("hello world\n")
     with open("testfolder/subfolder/test2.dat", "w") as upload_file: