fix: legible error on missing template placeholder (v0.2.1)

next() on a template source did template.format(...) directly, so a placeholder not
supplied in next(**fields) leaked a bare KeyError. catch KeyError/IndexError and
raise a clear ValueError naming the missing placeholder.

verified: next() without a required field -> ValueError naming it; happy path intact.
Signed-off-by: disqualifier <dev@disqualifier.me>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "aioproxies"
-version = "0.2.0"
+version = "0.2.1"
 description = "proxy parsing, formatting, health, and pool management for aiohttp/aioweb, camoufox, and socks5"
 requires-python = ">=3.10"
 dependencies = []

src/aioproxies/__init__.py

@@ -18,4 +18,4 @@ __all__ = [
     "to_proxy",
 ]
 
-__version__ = "0.2.0"
+__version__ = "0.2.1"

src/aioproxies/manager.py

@@ -123,7 +123,15 @@ class AioProxies:
         if self._static is not None:
             return self._static
         if self.template is not None:
-            return parse(self.template.format(session=self.session_id(), **fields))
+            try:
+                filled = self.template.format(session=self.session_id(), **fields)
+            except (KeyError, IndexError) as exc:
+                # a template placeholder wasn't supplied in next(**fields) — fail loud
+                # but legible instead of leaking a bare KeyError from str.format
+                raise ValueError(
+                    f"template placeholder {exc} not provided; pass it to next(**fields)"
+                ) from exc
+            return parse(filled)
         return self._next_from_list()
 
     def _next_from_list(self) -> Proxy: