introduce paths module which contains the data paths

This means that nominatim can find its data even when not called
from the command line tool.

CMakeLists.txt

@@ -233,7 +233,14 @@ if (BUILD_IMPORTER)
     install(DIRECTORY nominatim
             DESTINATION ${NOMINATIM_LIBDIR}/lib-python
             FILES_MATCHING PATTERN "*.py"
+            PATTERN "paths.py" EXCLUDE
             PATTERN __pycache__ EXCLUDE)
+
+    configure_file(${PROJECT_SOURCE_DIR}/cmake/paths-py.tmpl paths-py.installed)
+    install(FILES ${PROJECT_BINARY_DIR}/paths-py.installed
+            DESTINATION ${NOMINATIM_LIBDIR}/lib-python/nominatim
+            RENAME paths.py)
+
     install(DIRECTORY lib-sql DESTINATION ${NOMINATIM_LIBDIR})
 
     install(FILES ${COUNTRY_GRID_FILE}

cmake/paths-py.tmpl

@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2022 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Path settings for extra data used by Nominatim (installed version).
+"""
+from pathlib import Path
+
+PHPLIB_DIR = (Path('@NOMINATIM_LIBDIR@') / 'lib-php').resolve()
+SQLLIB_DIR = (Path('@NOMINATIM_LIBDIR@') / 'lib-sql').resolve()
+DATA_DIR = Path('@NOMINATIM_DATADIR@').resolve()
+CONFIG_DIR = Path('@NOMINATIM_CONFIGDIR@').resolve()

nominatim/paths.py

@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2022 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Path settings for extra data used by Nominatim.
+"""
+from pathlib import Path
+
+PHPLIB_DIR = (Path(__file__) / '..' / '..' / 'lib-php').resolve()
+SQLLIB_DIR = (Path(__file__) / '..' / '..' / 'lib-sql').resolve()
+DATA_DIR = (Path(__file__) / '..' / '..' / 'data').resolve()
+CONFIG_DIR = (Path(__file__) / '..' / '..' / 'settings').resolve()