new get_modem_pin function, which reads from multiple sources

sms_functions.py

@@ -24,6 +24,32 @@ class SIMError(ModemManagerError):
     def __str__(self):
         return repr(self.value)
 
+
+def get_modem_pin():
+
+    def read_modem_pin(path):
+        with open(path, 'r') as mp:
+            return mp.readline().rstrip('\n')
+    
+    # Check multiple paths
+    paths = [
+        os.path.join(
+            os.getcwd(),
+            'modem_pin.txt'
+        ),
+        os.path.join(
+            os.path.dirname(os.path.abspath(__file__)),
+            'modem_pin.txt'
+        ),
+        '/etc/modem_pin.txt'
+        ]
+
+    for p in paths:
+        if os.path.isfile(p):
+            return read_modem_pin(fpath)
+
+    raise Exception('modem_pin.txt not found in any directory')
+
 def get_modem():
         # Retry for 5 seconds and give the modems time
         retries = 0
@@ -56,17 +82,15 @@ def unlock_sim(modem):
     logger.debug("Modem status: {}".format(props))
     if props and props['state'] == 2:
         # check if the modem_pin.txt file exists
-        with open('modem_pin.txt', 'r') as mp:
-            mypin = mp.readline().rstrip('\n')
-            
-            logger.info("Trying to unlock %s", sim_path)
-            with SystemBus() as bus:
-                sim = bus.get('.ModemManager1', sim_path)
-                try:
-                    sim.SendPin(mypin, timeout=10000)
-                except GLib.Error as exc:
-                    remaining_attempts = modem.UnlockRetries
-                    raise SIMError('Failed to unlock PIN, remaining attempts: {}'.format(remaining_attempts)) from exc
+        mypin = get_modem_pin()
+        logger.info("Trying to unlock %s", sim_path)
+        with SystemBus() as bus:
+            sim = bus.get('.ModemManager1', sim_path)
+            try:
+                sim.SendPin(mypin, timeout=10000)
+            except GLib.Error as exc:
+                remaining_attempts = modem.UnlockRetries
+                raise SIMError('Failed to unlock PIN, remaining attempts: {}'.format(remaining_attempts)) from exc
 
 def unlock_and_enable_modem():