test-convert-darcs: skip if we can't find the elementtree module

This patch is a bit dirty to avoid having to repeat the dance required
to import elementtree.

hgext/convert/darcs.py

@@ -21,12 +21,17 b' class darcs_source(converter_source):'
     def __init__(self, ui, path, rev=None):
         super(darcs_source, self).__init__(ui, path, rev=rev)
 
-        if not os.path.exists(os.path.join(path, '_darcs', 'inventory')):
+        # check for _darcs, ElementTree, _darcs/inventory so that we can
+        # easily skip test-convert-darcs if ElementTree is not around
+        if not os.path.exists(os.path.join(path, '_darcs')):
             raise NoRepo("couldn't open darcs repo %s" % path)
 
         if ElementTree is None:
             raise util.Abort(_("Python ElementTree module is not available"))
 
+        if not os.path.exists(os.path.join(path, '_darcs', 'inventory')):
+            raise NoRepo("couldn't open darcs repo %s" % path)
+
         self.path = os.path.realpath(path)
 
         self.lastrev = None

tests/test-convert-darcs

@@ -9,6 +9,14 b" echo 'hgext.graphlog =' >> $HGRCPATH"
 DARCS_EMAIL='[e-mail]'; export DARCS_EMAIL
 HOME=do_not_use_HOME_darcs; export HOME
 
+# skip if we can't import elementtree
+mkdir dummy
+mkdir dummy/_darcs
+if hg convert dummy 2>&1 | grep ElementTree > /dev/null; then
+    echo 'hghave: missing feature: elementtree module'
+    exit 80
+fi
+
 echo % initialize darcs repo
 mkdir darcs-repo
 cd darcs-repo