tests: assert based on translated string

b/c updated in French translation later.

Note: the actual French string is
"L'utilisateur saisi n'existe pas en base" where the
apostrophes get rendered as ' in HTML and although the result
is translated the assertion fails.

As a workaround we'll not merge the commit introducing this
string ATM.

CC @RMadjev

tcms/testruns/tests/test_views.py

@@ -406,7 +406,7 @@ def test_refuse_to_remove_if_missing_user(self):
 
         self.assertContains(
             response,
-            'The user you typed does not exist in database')
+            _('The user you typed does not exist in database'))
 
         self.assert_cc(response, [self.cc_user_2, self.cc_user_3])
 
@@ -416,7 +416,7 @@ def test_refuse_to_add_if_missing_user(self):
 
         self.assertContains(
             response,
-            'The user you typed does not exist in database')
+            _('The user you typed does not exist in database'))
 
         self.assert_cc(response, [self.cc_user_2, self.cc_user_3])
 
@@ -427,7 +427,7 @@ def test_refuse_if_user_not_exist(self):
 
         self.assertContains(
             response,
-            'The user you typed does not exist in database')
+            _('The user you typed does not exist in database'))
 
         self.assert_cc(response, [self.cc_user_2, self.cc_user_3])