Don't warn about unused augmented assignments since they may have side effects (PY-14429)

python/src/com/jetbrains/python/inspections/PyUnusedLocalInspectionVisitor.java

@@ -125,6 +125,9 @@ public class PyUnusedLocalInspectionVisitor extends PyInspectionVisitor {
         if (PyImportStatementNavigator.getImportStatementByElement(element) != null) {
           continue;
         }
+        if (PyAugAssignmentStatementNavigator.getStatementByTarget(element) != null) {
+          continue;
+        }
         if (!myUsedElements.contains(element)) {
           myUnusedElements.add(element);
         }

python/testData/inspections/PyUnusedLocalVariableInspection/test.py

@@ -3,7 +3,7 @@ def foo1():
   <weak_warning descr="Local variable 'aaa' value is not used">aaa</weak_warning> = 2 #fail
 
   bbb = 1 #pass
-  <weak_warning descr="Local variable 'bbb' value is not used">bbb</weak_warning> += 2 #fail
+  return bbb
 
 def bar(<weak_warning descr="Parameter 'self' value is not used">self</weak_warning>): #fail
   print("Foo")
@@ -291,7 +291,7 @@ def test_unused_empty_function(<weak_warning descr="Parameter 'x' value is not u
 # PY-7072
 def test_unused_variable_in_cycle(x, c):
     while x > 0:
-        x -= 1 #pass
+        x = x - 1 #pass
         if c:
             break
 
@@ -316,3 +316,7 @@ def test_unused_empty_init_parameter():
 
     return C
 
+
+# PY-14429
+def test_used_local_augmented_assignment(x, y):
+    x += y