Use enums to describe target WPS state.

To avoid confusion about wps = True/False/None.
Came about because of #130

wifite/util/color.py

@@ -97,6 +97,10 @@ class Color(object):
         '''Prints an exception. Includes stack trace if necessary.'''
         Color.pl('\n{!} {R}Error: {O}%s' % str(exception))
 
+        # Don't dump trace for the "no targets found" case.
+        if 'No targets found' in str(exception):
+            return
+
         from ..config import Configuration
         if Configuration.verbose > 0 or Configuration.print_stack_traces:
             Color.pl('\n{!} {O}Full stack trace below')

wifite/util/scanner.py

@@ -4,7 +4,7 @@
 from ..util.color import Color
 from ..tools.airodump import Airodump
 from ..util.input import raw_input, xrange
-from ..model.target import Target
+from ..model.target import Target, WPSState
 from ..config import Configuration
 
 from time import sleep, time
@@ -88,7 +88,7 @@ class Scanner(object):
             return False  # No specific target from user.
 
         for target in self.targets:
-            if Configuration.wps_only and target.wps == False:
+            if Configuration.wps_only and target.wps not in [WPSState.UNLOCKED, WPSState.LOCKED]:
                 continue
             if bssid and target.bssid and bssid.lower() == target.bssid.lower():
                 self.target = target