Remove ignore_import_errors
    
    ignore_import_errors was added in 9b534238 to build FreeIPA ACI/API with
    some dependencies missing. It turns out that the import hook doesn't
    play nice with other meta importers or Cython-generated code like lxml:
    
    ./makeaci: ipaserver/plugins/dogtag.py:246: ignoring ImportError: No module named lxml.re
    Traceback (most recent call last):
      File "./makeaci", line 134, in <module>
        main(options)
      File "./makeaci", line 107, in main
        api.finalize()
      File "ipalib/plugable.py", line 733, in finalize
        self.__do_if_not_done('load_plugins')
      File "ipalib/plugable.py", line 425, in __do_if_not_done
        getattr(self, name)()
      File "ipalib/plugable.py", line 614, in load_plugins
        self.add_package(package)
      File "ipalib/plugable.py", line 641, in add_package
        module = importlib.import_module(name)
      File "/usr/lib64/python2.7/importlib/__init__.py", line 37, in import_module
        __import__(name)
      File "ipaserver/plugins/dogtag.py", line 246, in <module>
        from lxml import etree
      File "src/lxml/etree.pyx", line 93, in init lxml.etree
      File "src/lxml/_elementpath.py", line 58, in init lxml._elementpath
    AttributeError: 'FailedImport' object has no attribute 'compile'
    
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>