srp: remove 'pysrp' dependency

'pysrp' library includes 2 modules to implement SRP:

   * _ctsrp: Using OS libraries to implement SRP.
   * _pysrp: Pure Python implementation of SRP.

The first option is always '_ctsrp'. If there is any problem loading the
required libraries or looking for required methods inside, '_pysrp' is loaded.
This last module, '_pysrp' has a bug in the generation of the verifier for
certain combination of username and password (for example, user=apiservice,
password=1257c) See cocagne/pysrp#55.

This commit removes the dependency to 'pysrp' to avoid this bug and includes
the required implementation to calculate a salt and the corresponding verifier
to configure XBee Bluetooth password.

Signed-off-by: Tatiana Leon <Tatiana.Leon@digi.com>

Author: tatianaleon

CHANGELOG.rst

@@ -18,9 +18,18 @@ v1.4.2 - XX/XX/202X
 * Send/receive explicit data in 802.15.4.
   (XBee 3 modules support this feature)
 * Support for local and remote firmware update of XBee XR 868 and 900.
+* Remove 'pysrp' dependency:
+
+  * The library includes support to generate salt and verifier required to
+    configure '$S', '$V', '$W', '$X', and '$Y' XBee parameters to establish
+    Bluetooth password.
 * Bug fixing:
 
   * Fix order of nodes when creating a Zigbee source route (#278)
+  * Salt/verifier generation using 'pysrp' was not working with certain
+    passwords (see https://github.com/cocagne/pysrp/issues/55)
+    Solved by removing 'pysrp' dependency and implementing the code to
+    generate them.
 
 v1.4.1 - 12/22/2021
 -------------------

digi/xbee/devices.py

@@ -1,4 +1,4 @@
-# Copyright 2017-2022, Digi International Inc.
+# Copyright 2017-2024, Digi International Inc.
 #
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -1780,12 +1780,10 @@ def update_bluetooth_password(self, new_password, apply=True, save=True):
         if not isinstance(new_password, (str, bytes, bytearray)):
             raise ValueError("Password must be a string, bytes, or bytearray")
 
-        import srp
-
-        # Generate the salt and verifier using the SRP library.
-        salt, verifier = srp.create_salted_verification_key(
-            self._BLE_API_USERNAME, new_password, hash_alg=srp.SHA256,
-            ng_type=srp.NG_1024, salt_len=4)
+        import digi.xbee.util.srp
+        salt, verifier = digi.xbee.util.srp.create_salted_verification_key(
+            self._BLE_API_USERNAME, new_password, hash_alg=digi.xbee.util.srp.HAType.SHA256,
+            ng_type=digi.xbee.util.srp.NgGroupParams.NG_1024, salt_len=4)
 
         self.update_bluetooth_salt_verifier(salt, verifier, apply=apply, save=save)