If entering the first object level (i.e. the object
for which the browser has been started) fails, now
the error is raised directly (aborting the browser)
instead of running into an empty levels list later.
IPython/Extensions/ipipe.py (xiter): Make sure that iterating
a string containing a single line yields the string itself as the
only item.
IPython/Extensions/ibrowse.py (ibrowse): Avoid entering an
object if it's the same as the one on the last level (This avoids
infinite recursion for one line strings).