TempDir.join(unicode) returns unicode
TempDir.join(bytes) raises an Exception
FilePath(unicode) produces a text-mode FilePath
StorageServer.__init__ raises an exception if passed bytes

So we can just rely on self.tempdir.path being the correct type already and
even if it weren't StorageServer would immediately tell us.

Co-authored-by: Tom Prince <tom.prince@private.storage>

However, we still cannot be frozen (because of Failure.cleanFailure) and
cannot use attrs exception support (because we want value-based comparison).

They're all redundant on Python 3

and fix it

as Tahoe now wants, so it can respect available space when allocating more for
a lease

The version of versioneer has an issue that the tarball that is generated on
github changes, when the branches and/or tags refering to a commit change. This
causes issues for gridsync, which pins the hashes of those tarballs.

In addition to that, versioneer doesn't provide a meaningful revision for
untagged commits, when run from a github tarball.

Given that we only ever consume a github tarball as a github archive (except in
local development, where the version number is less important), this replaces
versioneer with some hand-rolled code specialized to that use case.

The later function takes a count of passes to generated, and passes
them to `make_passes`. This also changes `make_passes` to return `Pass`es,
which is what `get_passes` wants to receive.