tools: Make python_gut more correct.

- Using the ast module to correctly determine the line numbers
  of the function bodies.
- Should have done it this way in the beginning, but didn't know
  about ast module tracking line numbers.
- No more heuristics.
- Copes with different size indentations.

tests/gut_test.py

@@ -90,27 +90,16 @@ class GutTestCase(unittest.TestCase):
 
     def test_multiline_signature(self):
         program = textwrap.dedent("""
-            def bar(a, b
+            def bar(a, b,
                     c, d):
                 a = 1
             """)
         expected = textwrap.dedent("""
-            def bar(a, b
+            def bar(a, b,
                     c, d):
             """)
         self.assertEqual(gut.gut_module(program), expected)
 
-    def test_tab_in_indentation(self):
-        program = textwrap.dedent("""
-            def bar():
-                a = 1
-            \tb=2
-            """)
-        expected = textwrap.dedent("""
-            def bar():
-            """)
-        self.assertEqual(gut.gut_module(program), expected)
-
     def test_comment_in_signature_line(self):
         program = textwrap.dedent("""
             def bar(): # comment
@@ -142,9 +131,6 @@ class GutTestCase(unittest.TestCase):
             """)
         expected = textwrap.dedent("""
             def bar():
-
-            # comment
-                pass
             """)
         self.assertEqual(gut.gut_module(program), expected)
 
@@ -153,6 +139,7 @@ class GutTestCase(unittest.TestCase):
             def bar():
                 pass
                 pass
+
             # comment
             pass
             """)