merge

2 files changed, 11 insertions, 1 deletions

diff --git a/pygments/lexers/__init__.py b/pygments/lexers/__init__.py
index 7bcf3bf0..caedd479 100644
--- a/pygments/lexers/__init__.py
+++ b/pygments/lexers/__init__.py
@@ -82,6 +82,9 @@ def get_lexer_by_name(_alias, **options):
     """
     Get a lexer by an alias.
     """
+    if not _alias:
+        raise ClassNotFound('no lexer for alias %r found' % _alias)
+
     # lookup builtin lexers
     for module_name, name, aliases, _, _ in itervalues(LEXERS):
         if _alias.lower() in aliases:
diff --git a/tests/test_basic_api.py b/tests/test_basic_api.py
index e89b5c31..be7a4747 100644
--- a/tests/test_basic_api.py
+++ b/tests/test_basic_api.py
@@ -16,7 +16,7 @@ from pygments import lexers, formatters, filters, format
 from pygments.token import _TokenType, Text
 from pygments.lexer import RegexLexer
 from pygments.formatters.img import FontNotFound
-from pygments.util import text_type, StringIO, xrange
+from pygments.util import text_type, StringIO, xrange, ClassNotFound
 
 import support
 
@@ -138,6 +138,13 @@ def test_get_lexers():
         for mimetype in mimetypes:
             assert cls == lexers.get_lexer_for_mimetype(mimetype).__class__.__name__
 
+    try:
+        lexers.get_lexer_by_name(None)
+    except ClassNotFound:
+        pass
+    else:
+        raise Exception
+
 
 def test_formatter_public_api():
     ts = list(lexers.PythonLexer().get_tokens("def f(): pass"))