Remove a lot of unused imports

Signed-off-by: Daniel Narvaez <dwnarvaez@gmail.com>

tests/graphics/progressicon.py

@@ -23,7 +23,6 @@ Test the sugar3.graphics.progressicon.ProgressIcon widget.
 from gi.repository import GObject
 
 from sugar3.graphics.progressicon import ProgressIcon
-from sugar3.graphics.icon import Icon, get_surface
 from sugar3.graphics import style
 
 import common

tests/graphics/ticket2999.py

@@ -21,9 +21,6 @@ Spec in ticket #2999.
 
 from gi.repository import Gtk
 
-from sugar3.graphics.palette import Palette
-from sugar3.graphics.icon import Icon
-
 import common
 
 test = common.Test()

tests/lib/test_mime.py

@@ -17,7 +17,6 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
-import sys
 import unittest
 
 from sugar import mime