In python3 filter returns a generator instead of a list. When -4 or
-6 is used or if the host system has either of those address
families disabled len() gets called onto this filter expression
which results into a crash. This commit makes a filter expression
out of this statement and also adds a test for ipv4-only downloading.
When serving a `../` as directory (with `-l`), servefile creates an
endless 301-redirect loop. Having an absolute path fixes this. Since
this error might come up any time again, we're setting `targetDir` to
its absolute path right from the beginning and never have to worry about
it later on.
Sebastian Pipping
Sebastian Lohff
MasterofJOKers