Move ElementTree patching to be earlier (lyft#44)

This makes it OK for checkers to import ElementTree without adverse effects.

xiblint/__init__.py

@@ -1 +1 @@
-__version__ = '0.9.4'
+__version__ = '0.9.5'

xiblint/__main__.py

@@ -6,12 +6,10 @@
 import sys
 
 from xiblint import __version__
-from xiblint.config import Config
-from xiblint.xibcontext import XibContext
-import xiblint.rules
 
 
 def make_epilog_text():
+    import xiblint.rules
     description = "Lint rules:\n"
 
     for rule_name in sorted(xiblint.rules.rule_checkers.keys()):
@@ -26,6 +24,9 @@ def make_epilog_text():
 
 
 def main():
+    from patch_element_tree import patch_element_tree
+    patch_element_tree()
+
     parser = argparse.ArgumentParser(
         description='.xib / .storyboard linter',
         epilog=make_epilog_text(),
@@ -41,6 +42,7 @@ def main():
     args = parser.parse_args()
 
     try:
+        from xiblint.config import Config
         config = Config()
     except IOError as ex:
         print('Error: {}\n'.format(ex))
@@ -75,6 +77,7 @@ def main():
 
 
 def process_file(file_path, config):
+    from xiblint.xibcontext import XibContext
     checkers = config.checkers(file_path)
     context = XibContext(file_path)
     if context.tree:

xiblint/patch_element_tree.py

@@ -0,0 +1,5 @@
+def patch_element_tree():
+    # HACK to ensure cElementTree is not loaded -- we need the pure Python implementation
+    import sys
+    assert 'xml.etree.ElementTree' not in sys.modules
+    sys.modules['_elementtree'] = None  # type: ignore

xiblint/xmlutils.py

@@ -1,13 +1,7 @@
 import weakref
 
-# HACK to ensure cElementTree is not loaded -- we need the pure Python implementation
-import sys
-
-assert 'xml.etree.ElementTree' not in sys.modules
-sys.modules['_elementtree'] = None  # type: ignore
-
-from xml.etree import ElementTree  # noqa: E402
-from defusedxml.ElementTree import DefusedXMLParser  # noqa: E402
+from xml.etree import ElementTree
+from defusedxml.ElementTree import DefusedXMLParser
 
 
 class _TreeBuilder(ElementTree.TreeBuilder):