New cacheDir causes cache to be ignored(?)

it appears the Python client is incorrectly resolving path shortcuts such as '~'.
After setting syn.cache.cache_root_dir='~/asdfasdfasdf', f.path was still pointing to the '/Users/zdong/.synapseCache/' folder.

I then deleted the cache directories and used an absolute path for the cache:
syn.cache.cache_root_dir='/Users/zdong/asdfasdfasdf'
f.path now gives the correct cache location and the R client no longer redownloaded the file.

That is odd: the code specifically includes information to handle this:

also, the default cachdir includes the ~:

that only happens in the constructor. If the user manually assigns the variable it does not get expanded. I've overridden the _setattr_() to expand cache_root_dir