Skip test_feedparser_data if lxml_html_clean is not available

This is useful mostly for distributors shipping lxml without
lxml_html_clean.

src/lxml/html/tests/test_feedparser_data.py

@@ -9,7 +9,6 @@
 from lxml.tests.common_imports import doctest
 from lxml.doctestcompare import LHTMLOutputChecker
 
-from lxml.html.clean import clean, Cleaner
 
 feed_dirs = [
     os.path.join(os.path.dirname(__file__), 'feedparser-data'),
@@ -80,6 +79,12 @@ def shortDescription(self):
 
 def test_suite():
     suite = unittest.TestSuite()
+    try:
+        from lxml.html.clean import clean, Cleaner
+    except ImportError:
+        print("Skipping tests in feedparser_data - external lxml_html_clean package is not installed")
+        return suite
+
     for dir in feed_dirs:
         for fn in os.listdir(dir):
             fn = os.path.join(dir, fn)