[Findit & Predator] Code reorg of Findit.

appengine/predator/app/__init__.py

+import os
+import sys
+
+
+# Note: this hacky file will be excluded during deployment to AppEngine.
+# Add the checking of APPLICATION_ID is to avoid possible side-effect for local
+# AppEngine dev-server.
+
+if not os.environ.get('APPLICATION_ID'):  # pragma: no branch.
+  _THIS_DIR = os.path.dirname(os.path.realpath(__file__))
+
+  # This hack is due to testing setup and code structure.
+  #
+  # In testing setup, the root directory appengine/predator would be the current
+  # working directory during execution of unittests; and it is automatically
+  # added to sys.path or PYTHONPATH.
+  #
+  # For code structure, we wanted the AppEngine modules or services in separate
+  # sub-directories from the root directory in order to separate the code for
+  # AppEngine from those for the actual analysis -- core algorithm.
+  #
+  # With a module or service config file app.yaml or backend-*.yaml being in a
+  # sub-directory, that sub-directory would become the current working directory
+  # when the code is deployed to AppEngine or runs with AppEngine dev-server.
+  # This constraint requires that module importing in the code is based off the
+  # sub-directory.
+  #
+  # To avoid naming conflicts for module importing, we shouldn't put the *.yaml
+  # files to the sub-directories app/frontend and app/backend. Otherwise
+  # app/frontend and app/backend have to be added to sys.path or PYTHONPATH as
+  # explained above, and that will cause naming conflicts, because both of them
+  # will have same module names like handlers/, model/, etc.
+  #
+  # As the module or service config files *.yaml are in predator/app, it should
+  # be added to sys.path so that unittests won't complain about modules being
+  # not found.
+  sys.path.insert(0, _THIS_DIR)
+
+  # This hack is because the appengine_config.py is loaded by the testing setup
+  # only if it is in the root directory appengine/predator.
+  import appengine_config  # Unused Variable pylint: disable=W0612