Update package check in dev settings

A complete import of django-debug-toolbar and django_extensions was not
necessary, as we just wanted to check if the package was installed.
With newer versions of python (3.3+), we can use the
`importlib.util.find_spec`` function to check if a package is installed.

src/hub/settings/dev.py

@@ -67,9 +67,7 @@ EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'
 
 # configure debug_toolbar if it is installed and we're not testing
 if 'test' not in sys.argv:
-    try:
-        import debug_toolbar  # noqa: F401
-
+    if importlib.util.find_spec('debug_toolbar') is not None:
         INSTALLED_APPS += [  # noqa: F405
             'debug_toolbar',
         ]
@@ -88,9 +86,6 @@ if 'test' not in sys.argv:
         INTERNAL_IPS = [
             '127.0.0.1',
         ]
-    except ImportError:
-        pass
-
     if importlib.util.find_spec('django_watchfiles') is not None:
         INSTALLED_APPS += [  # noqa: F405
             'django_watchfiles',
@@ -99,10 +94,5 @@ if 'test' not in sys.argv:
 # configure extensions if they're available
 # allows to e.g. generate a PNG of the models' relationships:
 #   ./manage.py graph_models core -g -o ../models.png --disable-abstract-fields -X ContentType,PermissionsMixin,AbstractBaseUser,Group,Permission
-try:
-    import django_extensions  # noqa: F401
-
+if importlib.util.find_spec('django_extensions') is not None:
     INSTALLED_APPS = ['django_extensions', *INSTALLED_APPS]  # noqa: F405
-
-except ImportError:
-    pass