make use of nominatim-api in db package optional

src/nominatim_db/clicmd/__init__.py

@@ -13,16 +13,9 @@ Subcommand definitions for the command-line tool.
 
 from .setup import SetupAll as SetupAll
 from .replication import UpdateReplication as UpdateReplication
-from .api import (APISearch as APISearch,
-                  APIReverse as APIReverse,
-                  APILookup as APILookup,
-                  APIDetails as APIDetails,
-                  APIStatus as APIStatus)
 from .index import UpdateIndex as UpdateIndex
 from .refresh import UpdateRefresh as UpdateRefresh
 from .add_data import UpdateAddData as UpdateAddData
 from .admin import AdminFuncs as AdminFuncs
 from .freeze import SetupFreeze as SetupFreeze
 from .special_phrases import ImportSpecialPhrases as ImportSpecialPhrases
-from .export import QueryExport as QueryExport
-from .convert import ConvertDB as ConvertDB

src/nominatim_db/clicmd/admin.py

@@ -11,7 +11,7 @@ import logging
 import argparse
 import random
 
-import nominatim_api as napi
+from nominatim_core.errors import UsageError
 from nominatim_core.db.connection import connect
 from .args import NominatimArgs
 
@@ -95,6 +95,11 @@ class AdminFuncs:
 
 
     def _warm(self, args: NominatimArgs) -> int:
+        try:
+            import nominatim_api as napi
+        except ModuleNotFoundError as exp:
+            raise UsageError("Warming requires nominatim API. "
+                             "Install with 'pip install nominatim-api'.") from exp
         LOG.warning('Warming database caches')
 
         api = napi.NominatimAPI(args.project_dir)