The behavior of os.path.join() regarding path separators does not match the documentation. This affects Python 3.6, and goes back to at least Python 2.7.

From the documenation: 

"The return value is the concatenation of path and any members of *paths with exactly one directory separator (os.sep) following each non-empty part except the last, meaning that the result will only end in a separator if the last part is empty."

To me, this means that join will remove extraneous separators from the path, and that the only way to produce a trailing separator is to use join "" as the final path segment.

I expect `os.path.join("/abc//", "def/")` to produce the string "/abc/def" based on the documentation, but what it actually produces is "abc//def/".