Observed behavior
=================
Kernel tests will not run if python module pexpect is not installed
$ bitbake zephyr-kernel-test-all -ctestimage

ERROR: zephyr-kernel-test-test-nano-work-1.6.0-r0 do_testimage: Failed to import QemuTargetZephyr from available controller modules:
Traceback (most recent call last):
  File "/path/to/poky/meta/lib/oeqa/targetcontrol.py", line 32, in get_target_controller
    controller = getattr(sys.modules[__name__], testtarget)
AttributeError: module 'oeqa.targetcontrol' has no attribute 'QemuTargetZephyr'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/path/to/poky/meta/lib/oeqa/targetcontrol.py", line 38, in get_target_controller
    controller = testtargetloader.get_controller_module(testtarget, bbpath)
  File "/path/to/poky/meta/lib/oeqa/controllers/testtargetloader.py", line 15, in get_controller_module
    controller = self.load_controller_from_name(target, controllerslist)
  File "path/to/poky/meta/lib/oeqa/controllers/testtargetloader.py", line 48, in load_controller_from_name
    obj = self.load_controller_from_module(target, name)
  File "/path/to/poky/meta/lib/oeqa/controllers/testtargetloader.py", line 57, in load_controller_from_module
    module = __import__(modulename, globals(), locals(), [target])
  File "/path/to/poky/meta-yocto-bsp/lib/oeqa/controllers/beaglebonetarget.py", line 25, in <module>
    import pexpect
ImportError: No module named 'pexpect'

ERROR: zephyr-kernel-test-test-nano-work-1.6.0-r0 do_testimage: Function failed: do_testimage
ERROR: Logfile of failure stored in: /path/to/build/tmp/work/i586-yocto-elf/zephyr-kernel-test-test-nano-work/1.6.0-r0/temp/log.do_testimage.27044

Expected behavior
=================
Documentation states that python module pexpect must be installed.