support multiple wifi networks

CatToy.py

 ledTimerCallback(None)
 
 print("Initializing WiFi...")
-w = Wifi(Config.ssid, Config.password)
+w = Wifi(Config.networks)
 w.add_handler("/", rootCallback)
 w.add_handler("/servos", servoCallback)
 w.add_handler("/laser", laserCallback)

config.py

 class Config:
-# Set your wifi ssid and password here
-    ssid = const('')
-    password = const('')
+    networks = [
+        ("SSID_1", "PASS_1"),
+        ("SSID_2", "PASS_2"),
+    ]

wifi.py

     </html>
     """
 
-    def __init__(self, ssid, password, port = 80):
+    def __init__(self, networks, port = 80):
         # Check if wifi details have been set
-        if len(ssid) == 0 or len(password) == 0:
-            raise RuntimeError('Please set wifi ssid and password in config.py')
+        if len(networks) == 0:
             self.led.value(1)
+            raise RuntimeError('Please set wifi ssid and password in config.py')
 
         self.led = Pin("LED", Pin.OUT)
 
         # Start connection
         self.wlan = network.WLAN(network.STA_IF)
         self.wlan.active(True)
+        visible = self.wlan.scan()
+        ssid = None
+        password = None
+        for name, a, b, c, d, e in visible:
+            for t_ssid, t_password in networks:
+                if name.decode("utf-8") == t_ssid:
+                    ssid = t_ssid
+                    password = t_password
+                    break
+        if (ssid == None) or (password == None):
+            self.led.value(1)
+            raise RuntimeError("No known network found")
+
         self.wlan.connect(ssid, password)
 
         # Wait for connect success or failure
 
         # Handle connection error
         if self.wlan.status() != 3:
-            raise RuntimeError('wifi connection failed %d' % self.wlan.status())
             self.led.value(1)
+            raise RuntimeError('wifi connection failed %d' % self.wlan.status())
 
         print('connected')
         status = self.wlan.ifconfig()