PY-20038 Fixed: "Call to __init__ of super class is missed" inspection if super is used with __class__

Update PyMissingConstructorInspection to honour __class__ as a first arg of super(...).__init__ call

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

@@ -140,7 +140,8 @@ public class PyMissingConstructorInspection extends PyInspection {
                   String firstArg = args[0].getText();
                   final String qualifiedName = cl.getQualifiedName();
                   if (firstArg.equals(cl.getName()) || firstArg.equals(CANONICAL_SELF+"."+ __CLASS__) ||
-                      (qualifiedName != null && qualifiedName.endsWith(firstArg)))
+                      (qualifiedName != null && qualifiedName.endsWith(firstArg)) ||
+                      (LanguageLevel.forElement(cl).isAtLeast(LanguageLevel.PYTHON30) && firstArg.equals(__CLASS__)))
                       return true;
                   for (PyClass s : cl.getAncestorClasses(myTypeEvalContext)) {
                     if (firstArg.equals(s.getName()))

python/testData/inspections/PyMissingConstructorInspection/implicitDunderClass.py

@@ -0,0 +1,9 @@
+class First:
+    def __init__(self):
+        print('First inited')
+
+
+class Second(First):
+    def __init__(self):
+        super(__class__, self).__init__()
+        print('Second inited')

python/testSrc/com/jetbrains/python/inspections/PyMissingConstructorTest.java

@@ -44,7 +44,12 @@ public class PyMissingConstructorTest extends PyTestCase {
     doTest();
   }
 
-  public void testDunderClass() {  // PY-4038
+  public void testExplicitDunderClass() {  // PY-4038
+    doTest();
+  }
+
+  public void testImplicitDunderClass() {  // PY-20038
+    setLanguageLevel(LanguageLevel.PYTHON30);
     doTest();
   }