fixed #12 festival supports apostrophes again

phonemizer/festival.py

@@ -89,8 +89,13 @@ def _double_quoted(line):
 
 def _cleaned(line):
     """Remove 'forbidden' characters from the line"""
-    return line.replace('"', '').replace("'", '').replace(
-        '(', '').replace(')', '').strip()
+    # special case (very unlikely) where a line is only made of '
+    if len(set(line) - set("'")) == 0:
+        line = ''
+
+    # remove forbidden characters (reserved for scheme, ie festival
+    # scripting language)
+    return line.replace('"', '').replace('(', '').replace(')', '').strip()
 
 
 def _preprocess(text):

test/test_festival.py

@@ -18,10 +18,10 @@
 from phonemizer import festival, separator
 
 
-def _test(text):
+def _test(text, separator=separator.Separator(' ', '|', '-')):
     return festival.phonemize(
         text, language='en-us', strip=True,
-        separator=separator.Separator(' ', '|', '-'))
+        separator=separator)
 
 @pytest.mark.skipif(
     '2.1' in festival.festival_version(),
@@ -45,3 +45,10 @@ def test_its():
     assert _test("its") == ['ih-t-s']
     assert _test("it s") == ['ih-t eh-s']
     assert _test('it "s') == ['ih-t eh-s']
+
+def test_im():
+    sep = separator.Separator(' ', '', '')
+    assert _test("I'm looking for an image", sep) \
+        == ['aym luhkaxng faor axn ihmaxjh']
+    assert _test("Im looking for an image", sep) \
+        == ['ihm luhkaxng faor axn ihmaxjh']