generate_test_keys: minor improvements

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/scripts/generate_test_keys.py b/tests/scripts/generate_test_keys.py
index 9c5786d..1236baa 100755
--- a/tests/scripts/generate_test_keys.py
+++ b/tests/scripts/generate_test_keys.py
@@ -7,16 +7,12 @@
 generating the required key at run time. This helps speeding up testing."""
 
 import os
-import sys
 from typing import Iterator
 import re
-# pylint: disable=wrong-import-position
-SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__)) + "/"
-sys.path.append(SCRIPT_DIR + "../../scripts/")
-from mbedtls_dev.asymmetric_key_data import ASYMMETRIC_KEY_DATA
 import scripts_path # pylint: disable=unused-import
+from mbedtls_dev.asymmetric_key_data import ASYMMETRIC_KEY_DATA
 
-OUTPUT_HEADER_FILE = SCRIPT_DIR + "../src/test_keys.h"
+OUTPUT_HEADER_FILE = os.path.dirname(os.path.abspath(__file__)) + "/../src/test_keys.h"
 BYTES_PER_LINE = 16
 
 def c_byte_array_literal_content(array_name: str, key_data: bytes) -> Iterator[str]:
@@ -53,25 +49,25 @@
 # - understand if the curve is supported in legacy symbols (MBEDTLS_ECP_DP_...)
 EC_NAME_CONVERSION = {
     'PSA_ECC_FAMILY_SECP_K1': {
-        192: ['secp', 'k1'],
-        224: ['secp', 'k1'],
-        256: ['secp', 'k1']
+        192: ('secp', 'k1'),
+        224: ('secp', 'k1'),
+        256: ('secp', 'k1')
     },
     'PSA_ECC_FAMILY_SECP_R1': {
-        192: ['secp', 'r1'],
-        224: ['secp', 'r1'],
-        256: ['secp', 'r1'],
-        384: ['secp', 'r1'],
-        521: ['secp', 'r1']
+        192: ('secp', 'r1'),
+        224: ('secp', 'r1'),
+        256: ('secp', 'r1'),
+        384: ('secp', 'r1'),
+        521: ('secp', 'r1')
     },
     'PSA_ECC_FAMILY_BRAINPOOL_P_R1': {
-        256: ['bp', 'r1'],
-        384: ['bp', 'r1'],
-        512: ['bp', 'r1']
+        256: ('bp', 'r1'),
+        384: ('bp', 'r1'),
+        512: ('bp', 'r1')
     },
     'PSA_ECC_FAMILY_MONTGOMERY': {
-        255: ['curve', '19'],
-        448: ['curve', '']
+        255: ('curve', '19'),
+        448: ('curve', '')
     }
 }
 
@@ -80,13 +76,13 @@
     try:
         prefix = EC_NAME_CONVERSION[ec_family][bits][0]
         suffix = EC_NAME_CONVERSION[ec_family][bits][1]
-    except: # pylint: disable=bare-except
+    except KeyError:
         return ""
     return prefix + str(bits) + suffix
 
 def get_look_up_table_entry(key_type: str, curve_or_keybits: str,
                             priv_array_name: str, pub_array_name: str) -> Iterator[str]:
-    yield "\n    {{ {}, ".format("1" if key_type == "ec" else "0")
+    yield "    {{ {}, ".format("1" if key_type == "ec" else "0")
     yield "{},\n".format(curve_or_keybits)
     yield "      {0}, sizeof({0}),\n".format(priv_array_name)
     yield "      {0}, sizeof({0}) }},".format(pub_array_name)
@@ -104,12 +100,12 @@
         " *********************************************************************************/\n"
     )
 
-    look_up_table = ""
+    look_up_table = []
 
     # Get a list of private keys only in order to get a single item for every
     # (key type, key bits) pair. We know that ASYMMETRIC_KEY_DATA
     # contains also the public counterpart.
-    priv_keys = [key for key in ASYMMETRIC_KEY_DATA if re.match(r'.*_KEY_PAIR', key)]
+    priv_keys = [key for key in ASYMMETRIC_KEY_DATA if '_KEY_PAIR' in key]
 
     for priv_key in priv_keys:
         key_type = get_key_type(priv_key)
@@ -142,9 +138,8 @@
                 curve_or_keybits = "MBEDTLS_ECP_DP_" + curve.upper()
             else:
                 curve_or_keybits = str(bits)
-            look_up_table = look_up_table + \
-                            ''.join(get_look_up_table_entry(key_type, curve_or_keybits,
-                                                            array_name_priv, array_name_pub))
+            look_up_table.append(''.join(get_look_up_table_entry(key_type, curve_or_keybits,
+                                                                 array_name_priv, array_name_pub)))
     # Write the lookup table: the struct containing pointers to all the arrays we created above.
     output_file.write("""
 struct predefined_key_element {
@@ -156,8 +151,10 @@
     size_t pub_key_len;
 };
 
-struct predefined_key_element predefined_keys[] = {""")
-    output_file.write("{}\n}};\n".format(look_up_table))
+struct predefined_key_element predefined_keys[] = {
+""")
+    output_file.write("\n".join(look_up_table))
+    output_file.write("\n};\n")
 
 if __name__ == '__main__':
     main()