Fixed BNF concept evaluations

tests/test_utils.py

@@ -125,6 +125,11 @@ def test_i_can_strip_eof():
     assert actual == expected
 
 
+def test_i_can_escape():
+    actual = core.utils.escape_char("hello 'world' my friend", "'")
+    assert actual == "hello \\'world\\' my friend"
+
+
 def get_tokens(lst):
     res = []
     for e in lst: