Django: Instrumentation can get activated even when django not in use

[pglombardo]

Just having the Django package in sys.modules (but without a running Django app) causes the following cosmetic error:

2019-10-17 12:24:28,705: 1 DEBUG instana: Instrumenting django
2019-10-17 12:24:28,944: 1 DEBUG instana: django.middleware:
Traceback (most recent call last):
  File "/tmp/instana/python/instana/instrumentation/django/middleware.py", line 133, in <module>
    wsgiapp = get_internal_wsgi_application()
  File "/usr/local/lib/python2.7/site-packages/django/core/servers/basehttp.py", line 42, in get_internal_wsgi_application
    app_path = getattr(settings, 'WSGI_APPLICATION')
  File "/usr/local/lib/python2.7/site-packages/django/conf/__init__.py", line 56, in __getattr__
    self._setup(name)
  File "/usr/local/lib/python2.7/site-packages/django/conf/__init__.py", line 39, in _setup
    % (desc, ENVIRONMENT_VARIABLE))
ImproperlyConfigured: Requested setting WSGI_APPLICATION, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.