utils/log: add indentcontext

Add indentcontext context manager to save having to add try/finally
clauses around indenting code just to ensure dedenting.

wa/utils/log.py

@@ -21,6 +21,7 @@ import os
 import string
 import subprocess
 import threading
+from contextlib import contextmanager
 
 import colorama
 
@@ -148,6 +149,15 @@ def dedent():
     _indent_level -= 1
 
 
+@contextmanager
+def indentcontext():
+    indent()
+    try:
+        yield
+    finally:
+        dedent()
+
+
 def set_indent_level(level):
     global _indent_level
     old_level = _indent_level