Fix not-used-before-assignment false positive (#1266)

pylint/checkers/variables.py

@@ -901,8 +901,9 @@ def _is_variable_violation(node, name, defnode, stmt, defstmt,
         else:
             # we are in a local scope, check the name is not
             # defined in global or builtin scope
-            # skip this lookup if name is assigned later in given scope
-            if not _assigned_locally(node) and defframe.root().lookup(name)[1]:
+            # skip this lookup if name is assigned later in function scope
+            forbid_lookup = isinstance(frame, astroid.FunctionDef) and _assigned_locally(node)
+            if not forbid_lookup and defframe.root().lookup(name)[1]:
                 maybee0601 = False
             else:
                 # check if we have a nonlocal

pylint/test/functional/used_before_assignment_issue1081.py

@@ -1,4 +1,4 @@
-# pylint: disable=missing-docstring,invalid-name
+# pylint: disable=missing-docstring,invalid-name,too-few-public-methods
 
 x = 24
 
@@ -30,3 +30,11 @@ def not_used_before_assignment_2(a):
     x = 3  # [redefined-outer-name]
     if x == a:
         pass
+
+
+def func(something):
+    return something ** 3
+
+
+class FalsePositive(object):
+    x = func(x)