feat: raise any httpx exceptions, e.g. from failed auth

This means that 403s, such as those from not being allowed to fetch a specific
version, are passed to client code, and so help debug permission errors better
than the disk i/o error that's being raised right now.

It also means there is consistency - before this change if there's a 403 (or
any other connection error) from the initial HEAD request on the start of a
query, then that was being passed to client now. Now, during the read data
during the query if these get raised they get passed to client code.

sqlite_s3_query.py

@@ -69,13 +69,25 @@ def sqlite_s3_query_multi(url, get_credentials=lambda now: (
     body_hash = sha256(b'').hexdigest()
     scheme, netloc, path, _, _ = urlsplit(url)
 
+    pending_exception = None
+
+    def raise_any_pending_exception():
+        nonlocal pending_exception
+        if pending_exception is not None:
+            to_raise = pending_exception
+            pending_exception = None
+            raise to_raise
+
     def run(func, *args):
         res = func(*args)
+        raise_any_pending_exception()
         if res != 0:
             raise SQLiteError(libsqlite3.sqlite3_errstr(res).decode())
 
     def run_with_db(db, func, *args):
-        if func(*args) != 0:
+        res = func(*args)
+        raise_any_pending_exception()
+        if res != 0:
             raise SQLiteError(libsqlite3.sqlite3_errmsg(db).decode())
 
     @contextmanager
@@ -169,6 +181,7 @@ def x_close(p_file):
 
         x_read_type = CFUNCTYPE(c_int, c_void_p, c_void_p, c_int, c_int64)
         def x_read(p_file, p_out, i_amt, i_ofst):
+            nonlocal pending_exception
             offset = 0
 
             try:
@@ -183,7 +196,8 @@ def x_read(p_file, p_out, i_amt, i_ofst):
                         offset += len(chunk)
                         if offset > i_amt:
                             break
-            except Exception:
+            except Exception as exception:
+                pending_exception = exception
                 return SQLITE_IOERR
 
             if offset != i_amt: