buildhistory: skip tests if GitPython module is missing
Catching a possible exception when importing the git module,
allows us to skip test if the latter is missing on the host.
Also, import oe.buildhistory_analysis inside fuctions
because this module also needs git to work correctly.
[YOCTO #11620]
Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
