PY-32472: Skip "unused" inspection for Django implicit contract signatures

User may have View.get method with unused parameters, which are, however, required.

python/intellij.python.community.impl.iml

@@ -32,5 +32,6 @@
     <orderEntry type="library" name="netty-handler" level="project" />
     <orderEntry type="library" name="netty-codec-http" level="project" />
     <orderEntry type="library" name="jsoup" level="project" />
+    <orderEntry type="module" module-name="intellij.platform.extensions" scope="PROVIDED" />
   </component>
 </module>

python/src/META-INF/python-core-common.xml

@@ -669,6 +669,7 @@
   </extensions>
 
   <extensionPoints>
+    <extensionPoint qualifiedName="Pythonid.skipUnusedLocal" interface="com.jetbrains.python.inspections.PyUnusedLocalInspectionSkipper"/>
     <extensionPoint qualifiedName="Pythonid.pyReferenceCustomTargetChecker" interface="com.jetbrains.python.psi.impl.references.PyReferenceCustomTargetChecker"/>
     <extensionPoint qualifiedName="Pythonid.pyTestFixtureExtension" interface="com.jetbrains.python.testing.pyTestFixtures.PyTestFixtureExtension"/>
     <extensionPoint qualifiedName="Pythonid.pyTestConfigurationSelector"  interface="com.jetbrains.python.testing.PyTestConfigurationSelector"/>

python/src/com/jetbrains/python/inspections/PyUnusedLocalInspectionSkipper.kt

@@ -0,0 +1,16 @@
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.jetbrains.python.inspections
+
+import com.intellij.openapi.extensions.ExtensionPointName
+import com.jetbrains.python.psi.PyFunction
+import com.jetbrains.python.psi.types.TypeEvalContext
+
+interface PyUnusedLocalInspectionSkipper {
+  fun skip(element: PyFunction, context: TypeEvalContext): Boolean
+
+  companion object {
+    fun skip(element: PyFunction,
+             context: TypeEvalContext) = EP.extensions.any { it.skip(element, context) }
+    val EP = ExtensionPointName.create<PyUnusedLocalInspectionSkipper>("Pythonid.skipUnusedLocal")
+  }
+}

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

@@ -67,8 +67,8 @@ public class PyUnusedLocalInspectionVisitor extends PyInspectionVisitor {
   }
 
   @Override
-  public void visitPyFunction(final PyFunction node) {
-    if (!PyiUtil.isOverload(node, myTypeEvalContext)) {
+  public void visitPyFunction(@NotNull final PyFunction node) {
+    if (!PyiUtil.isOverload(node, myTypeEvalContext) && !PyUnusedLocalInspectionSkipper.Companion.skip(node, myTypeEvalContext)) {
       processScope(node);
     }
   }