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>

Makefile.am

@@ -14,16 +14,13 @@ SUBDIRS = asn1 util client contrib po pypi \
 	$(IPACLIENT_SUBDIRS) ipaplatform $(IPATESTS_SUBDIRS) $(SERVER_SUBDIRS)
 
 MOSTLYCLEANFILES = ipasetup.pyc ipasetup.pyo \
-		   ignore_import_errors.pyc ignore_import_errors.pyo \
-		   ipasetup.pyc ipasetup.pyo \
 		   pylint_plugins.pyc pylint_plugins.pyo
 
 # user-facing scripts
 dist_bin_SCRIPTS = ipa
 
 # files required for build but not installed
-dist_noinst_SCRIPTS = ignore_import_errors.py \
-		      makeapi \
+dist_noinst_SCRIPTS = makeapi \
 		      makeaci \
 		      make-doc \
 		      make-test \