meson: use fallback import path in start script

Pass the module install path to the start script and add it to sys.path
if import fails.

bin/meson.build

@@ -2,6 +2,7 @@ bin_conf = configuration_data()
 bin_conf.set('appid', appid)
 bin_conf.set('pkgdatadir', join_paths(prefix, pkgdatadir))
 bin_conf.set('python_major_ver', python_major_ver)
+bin_conf.set('purelib_path', join_paths(prefix, purelib_path))
 
 configure_file(
     input: 'pulseaudio-equalizer-gtk.in',

bin/pulseaudio-equalizer-gtk.in

@@ -7,6 +7,15 @@ resource = Gio.resource_load(
     os.path.join('@pkgdatadir@', '@appid@.gresource'))
 Gio.Resource._register(resource)
 
+try:
+    __import__('importlib').import_module('pulseeq')
+except ImportError:
+    sys.path.append('@purelib_path@')
+    try:
+        __import__('importlib').import_module('pulseeq')
+    except ImportError:
+        raise
+
 from pulseeq import equalizer
 
 app = equalizer.Application()

meson.build

@@ -18,6 +18,14 @@ pythondir = python.get_path('purelib')
 pkgdatadir = join_paths(datadir, meson.project_name())
 appdir = join_paths(pythondir, modname)
 
+purelib_option = get_option('purelib')
+
+if not (purelib_option == '')
+    purelib_path = purelib_option
+else
+    purelib_path = python.get_install_dir()
+endif
+
 subdir('bin')
 subdir('data')
 subdir(modname)

pulseeq/meson.build

@@ -11,7 +11,7 @@ equalizer_sources = ['__init__.py', 'equalizer.py', constants_file]
 
 purelib_path = get_option('purelib')
 
-if not (purelib_path == '')
+if not (purelib_option == '')
     install_data(equalizer_sources,
         install_dir: join_paths(purelib_path, modname)
     )