The new rbtools.diffs.patches.Patch represents a patch that can be

applied to a source tree. It consists of patch content or a patch file

path, along with optional information needed to apply the patch, such as

the commit author and message, base directory, and path prefix strip

level.
To access the contents of a Patch, you first call open(). This is a

context manager that ensures you can get to the content or file path,

and that any temporary state is then cleaned up after use.
A Patch can also be assigned to a PatchResult. This is optional,

but will let a receiver of a PatchResult access information on the

underlying Patch.
Currently, Patch isn't being used, but it will form a key part of the

upcoming work on how patches get applied to repositories.

Unit tests pass.
Tested this in some in-progress patching code.