Unfortunately http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=415fbfb0cd1bc5129179596ba27ae2362b7de2a4 has caused a regression - it can't work with memory resident bitbake, since it attempts to call functions defined in the metadata on the UI side instead of in the bitbake server with the following result:

------------ snip ------------
$ recipetool create -V 2.4.2 -N mbedtls https://tls.mbed.org/download/start/mbedtls-2.4.2-apache.tgz
NOTE: Fetching https://tls.mbed.org/download/start/mbedtls-2.4.2-apache.tgz...
ERROR: Error executing a python function in exec_python_func() autogenerated:

The stack trace of python calls that resulted in this exception/failure was:
File: 'exec_python_func() autogenerated', lineno: 2, function: <module>
     0001:
 *** 0002:extend_recipe_sysroot(d)
     0003:
File: '/home/paul/poky/poky/meta/classes/staging.bbclass', lineno: 350, function: extend_recipe_sysroot
     0346:    # Detect bitbake -b usage
     0347:    nodeps = d.getVar("BB_LIMITEDDEPS") or False
     0348:    if nodeps:
     0349:        lock = bb.utils.lockfile(recipesysroot + "/sysroot.lock")
 *** 0350:        staging_populate_sysroot_dir(recipesysroot, recipesysrootnative, True, d)
     0351:        staging_populate_sysroot_dir(recipesysroot, recipesysrootnative, False, d)
     0352:        bb.utils.unlockfile(lock)
     0353:        return
     0354:
Exception: NameError: name 'staging_populate_sysroot_dir' is not defined
...

------------ snip ------------

It could be that we should fix this at the same time as bug 11198 as executing this as more traditional do_fetch + do_unpack tasks would bypass the problem.