The code to split a path and normalize repeated slashes for Subversion

URLs was using a regex that wasn't very safe. It was splitting on /*,

which means 0 or more slashes. Python 3 warned about this, but kept

behavior the same. Python 3.7 removed the backwards-compatibility, and

the result was that every single character was split into its own item

in an array.
This fixes the regex to be /+, which is the correct form of what we

wanted, fixing compatibility with all Python versions.

Unit tests pass on all supported versions of Python.