[1.5.x] Fixed #20773 -- [gis] Fixed regression in GoogleMap output

Thanks Martyn Clement for the report and the initial patch.
Backport of 27c1a72 from master.

django/contrib/gis/maps/google/gmap.py

@@ -134,7 +134,8 @@ def js(self):
     @property
     def scripts(self):
         "Returns all <script></script> tags required with Google Maps JavaScript."
-        return format_html('%s\n  <script type="text/javascript">\n//<![CDATA[\n%s//]]>\n  </script>', self.api_script, mark_safe(self.js))
+        return format_html('{0}\n  <script type="text/javascript">\n//<![CDATA[\n{1}//]]>\n  </script>',
+                           self.api_script, mark_safe(self.js))
 
     @property
     def style(self):

django/contrib/gis/tests/geoadmin/tests.py

@@ -1,11 +1,14 @@
 from __future__ import absolute_import
 
-from django.test import TestCase
 from django.contrib.gis import admin
 from django.contrib.gis.geos import GEOSGeometry, Point
+from django.test import TestCase
+from django.test.utils import override_settings
 
 from .models import City
 
+GOOGLE_MAPS_API_KEY = 'XXXX'
+
 
 class GeoAdminTest(TestCase):
     urls = 'django.contrib.gis.tests.geoadmin.urls'
@@ -35,7 +38,9 @@ def test_olmap_WMS_rendering(self):
             result)
 
     def test_olwidget_has_changed(self):
-        """ Check that changes are accurately noticed by OpenLayersWidget. """
+        """
+        Check that changes are accurately noticed by OpenLayersWidget.
+        """
         geoadmin = admin.site._registry[City]
         form = geoadmin.get_changelist_form(None)()
         has_changed = form.fields['point'].widget._has_changed
@@ -51,3 +56,15 @@ def test_olwidget_has_changed(self):
         self.assertFalse(has_changed(initial, data_same))
         self.assertFalse(has_changed(initial, data_almost_same))
         self.assertTrue(has_changed(initial, data_changed))
+
+    @override_settings(GOOGLE_MAPS_API_KEY=GOOGLE_MAPS_API_KEY)
+    def test_google_map_scripts(self):
+        """
+        Testing GoogleMap.scripts() output. See #20773.
+        """
+        from django.contrib.gis.maps.google.gmap import GoogleMap
+
+        google_map = GoogleMap()
+        scripts = google_map.scripts
+        self.assertIn(GOOGLE_MAPS_API_KEY, scripts)
+        self.assertIn("new GMap2", scripts)