imgtool: Add filename to some common prints

Common prints such as the one that happens when an image is signed
are clearer if the source of print is added (i.e. filename), especially
for those build integration flows where imgtool is invoked as part of
a set of operations.

Signed-off-by: Antonio de Angelis <Antonio.deAngelis@arm.com>

Author: adeaarm

scripts/imgtool/image.py

@@ -315,7 +315,7 @@ def create(self, key, public_key_format, enckey, dependencies=None,
             pubbytes = sha.digest()
         elif pub_key is not None:
             if hasattr(pub_key, 'sign'):
-                print("sign the payload")
+                print(os.path.basename(__file__) + ": sign the payload")
             pub = pub_key.get_public_bytes()
             sha = hashlib.sha256()
             sha.update(pub)
@@ -443,22 +443,22 @@ def create(self, key, public_key_format, enckey, dependencies=None,
             if vector_to_sign == 'payload':
                 # Stop amending data to the image
                 # Just keep data vector which is expected to be sigend
-                print('export payload')
+                print(os.path.basename(__file__) + ': export payload')
                 return
             elif vector_to_sign == 'digest':
                 self.payload = digest
-                print('export digest')
+                print(os.path.basename(__file__) + ': export digest')
                 return
 
             if key is not None and fixed_sig is None:
                 # `sign` expects the full image payload (sha256 done internally),
                 # while `sign_digest` expects only the digest of the payload
 
                 if hasattr(key, 'sign'):
-                    print("sign the payload")
+                    print(os.path.basename(__file__) + ": sign the payload")
                     sig = key.sign(bytes(self.payload))
                 else:
-                    print("sign the digest")
+                    print(os.path.basename(__file__) + ": sign the digest")
                     sig = key.sign_digest(digest)
                 tlv.add(key.sig_tlv(), sig)
                 self.signature = sig