Fix missing f-string prefixes on error messages

Strings with {variable} interpolation were missing the f prefix,
causing the literal text "{variable}" to appear in error messages
instead of the variable's value.

- bcur.py:88 — BCURStringFormatError message
- descriptor.py:81,85 — ValueError messages (2 instances)
- hd.py:712 — ValueError message
- psbt.py:776 — SuspiciousTransaction message

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jimmysong

buidl/bcur.py

@@ -85,7 +85,7 @@ def _parse_bcur_helper(bcur_string):
         y_int = int(xofy_parts[1])
 
         if x_int > y_int:
-            raise BCURStringFormatError("x must be >= y (in x-of-y): {xofy_parts}")
+            raise BCURStringFormatError(f"x must be >= y (in x-of-y): {xofy_parts}")
 
     else:
         raise BCURStringFormatError(f"{string} doesn't have 2-4 slashes")

buidl/descriptor.py

@@ -78,11 +78,11 @@ def parse_full_key_record(key_record_str):
     parts = key_record_str.split("/")
     if parts[-1] != "*":
         raise ValueError(
-            "Invalid full key record, does not end with a *: {key_record_str}"
+            f"Invalid full key record, does not end with a *: {key_record_str}"
         )
     if not is_intable(parts[-2]):
         raise ValueError(
-            "Invalid full key record, account index `{parts[-2]}` is not an int: {key_record_str}"
+            f"Invalid full key record, account index `{parts[-2]}` is not an int: {key_record_str}"
         )
 
     # Now we strip off the trailing account index and *, and parse the rest as a partial key record

buidl/hd.py

@@ -709,7 +709,7 @@ def raw_parse(cls, s, network=None):
         elif pub_version in ALL_MAINNET_XPUBS:
             network = "mainnet"
         else:
-            raise ValueError("not a valid [t-z]pub pub_version: {pub_version}")
+            raise ValueError(f"not a valid [t-z]pub pub_version: {pub_version}")
         # the next byte is depth
         depth = byte_to_int(s.read(1))
         # next 4 bytes are the parent_fingerprint

buidl/psbt.py

@@ -773,7 +773,7 @@ def _describe_basic_multisig_inputs(self, hdpubkey_map):
 
         if not root_paths_for_signing:
             raise SuspiciousTransaction(
-                "No `root_paths_for_signing` with `hdpubkey_map` {hdpubkey_map} in PSBT:\n{self}"
+                f"No `root_paths_for_signing` with `hdpubkey_map` {hdpubkey_map} in PSBT:\n{self}"
             )
 
         return {