Fixes robotframework#629 by expecting NoSuchElementException (robotframework#630)

* Fixes robotframework#629 by expecting NoSuchElementException

Empty expect are not coding practices. The deselect_by_value
and the deselect_by_visible_text raises NoSuchElementException if it
can not deselect the items.

Author: aaltat

src/Selenium2Library/keywords/_selectelement.py

@@ -1,5 +1,7 @@
 from selenium.webdriver.support.ui import Select
 from keywordgroup import KeywordGroup
+from selenium.common.exceptions import NoSuchElementException
+
 
 class _SelectElementKeywords(KeywordGroup):
 
@@ -271,17 +273,16 @@ def unselect_from_list(self, locator, *items):
 
         select, options = self._get_select_list_options(select)
         for item in items:
+            # Only Selenium 2.52 and newer raise exceptions when there is no match.
+            # For backwards compatibility reasons we want to ignore them.
             try:
                 select.deselect_by_value(item)
-                # Code for selenium <= 2.52.0
+            except NoSuchElementException:
+                pass
+            try:
                 select.deselect_by_visible_text(item)
-            except:  # Code for selenium > 2.52.0
-                try:
-                    select.deselect_by_visible_text(item)
-                except:
-                    self._warn("Tried to unselect missing selection item, \
-'%s' from locator '%s'." % (item, locator))
-                    continue
+            except NoSuchElementException:
+                pass
 
     def unselect_from_list_by_index(self, locator, *indexes):
         """Unselects `*indexes` from list identified by `locator`