Fix #2253: `:pyobject: option of literalinclude` directive can't detect indented body block when the block starts with blank or comment lines.

tests/roots/test-directive-code/python.rst

@@ -0,0 +1,13 @@
+===========================
+Literal Includes for python
+===========================
+
+block start with blank or comment
+=================================
+
+.. literalinclude:: target.py
+   :pyobject: block_start_with_comment
+
+.. literalinclude:: target.py
+   :pyobject: block_start_with_blank
+

tests/roots/test-directive-code/target.py

@@ -0,0 +1,22 @@
+# Literally included file using Python highlighting
+# -*- coding: utf-8 -*-
+
+foo = "Including Unicode characters: üöä"
+
+class Foo:
+    pass
+
+class Bar:
+    def baz():
+        pass
+
+# comment after Bar class definition
+def bar(): pass
+
+def block_start_with_comment():
+    # Comment
+    return 1
+
+def block_start_with_blank():
+
+    return 1