the mechanism for setting an SDK through project userdata isn't needed anymore, and most likely was never used

python/src/com/jetbrains/python/psi/impl/PyBuiltinCache.java

@@ -1,6 +1,5 @@
 package com.jetbrains.python.psi.impl;
 
-import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.module.Module;
 import com.intellij.openapi.module.ModuleUtil;
 import com.intellij.openapi.project.Project;
@@ -47,11 +46,6 @@ public class PyBuiltinCache {
 
   private PyType STRING_TYPE_PY2 = null;
 
-  /**
-   * Used in cases when a virtual file as absent in test mode; then the project may store its own SDK.
-   */
-  public static final Key<Sdk> TEST_SDK = new Key<Sdk>("test.sdk.instance");
-
   /**
    * Returns an instance of builtin cache. Instances differ per module and are cached.
    * @param reference something to define the module from.
@@ -96,10 +90,6 @@ public class PyBuiltinCache {
           }
         }
       }
-      else if (ApplicationManager.getApplication().isUnitTestMode()) {
-        // did they store a test SDK for us?
-        sdk = project.getUserData(TEST_SDK);
-      }
     }
     return sdk;
   }