[sonic-host-services]: Fix import and invalid path (#10660)

Why I did it
Can not start sonic-hostservice

How I did it
Install python3-dbus and systemd-python, and replace invalid path

How to verify it
Start the service with below commands:
sudo systemctl start sonic-hostservice
sudo systemctl status sonic-hostservice

Signed-off-by: Gang Lv ganglv@microsoft.com

files/build_templates/sonic_debian_extension.j2

@@ -233,7 +233,10 @@ sudo cp -f $IMAGE_CONFIGS/bash/bash.bashrc $FILESYSTEM_ROOT/etc/
 sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install libcairo2-dev libdbus-1-dev libgirepository1.0-dev libsystemd-dev pkg-config
 
 # Mark runtime dependencies as manually installed to avoid them being auto-removed while uninstalling build dependencies
-sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-mark manual gir1.2-glib-2.0 libdbus-1-3 libgirepository-1.0-1 libsystemd0
+sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-mark manual gir1.2-glib-2.0 libdbus-1-3 libgirepository-1.0-1 libsystemd0 python3-dbus
+
+# Install systemd-python for SONiC host services
+sudo https_proxy=$https_proxy LANG=C chroot $FILESYSTEM_ROOT pip3 install systemd-python
 
 # Install SONiC host services package
 SONIC_HOST_SERVICES_PY3_WHEEL_NAME=$(basename {{sonic_host_services_py3_wheel_path}})

src/sonic-host-services/scripts/sonic-host-server

@@ -13,9 +13,16 @@ import dbus.mainloop.glib
 
 from gi.repository import GObject
 
-def register_modules():
+def find_module_path():
+    """Find path for host_moduels"""
+    try:
+        from host_modules import host_service
+        return os.path.dirname(host_service.__file__)
+    except ImportError as e:
+        return None
+
+def register_modules(mod_path):
     """Register all host modules"""
-    mod_path = '/usr/local/lib/python3.7/dist-packages/host_modules'
     sys.path.append(mod_path)
     for mod_file in glob.glob(os.path.join(mod_path, '*.py')):
         if os.path.isfile(mod_file) and not mod_file.endswith('__init__.py'):
@@ -62,7 +69,9 @@ class SignalManager(object):
         loop.quit()
 
 sigmgr = SignalManager()
-register_modules()
+mod_path = find_module_path()
+if mod_path is not None:
+    register_modules(mod_path)
 
 # Only run if we actually have some handlers
 if handlers:

src/sonic-host-services/setup.py

@@ -24,6 +24,7 @@
     ],
     install_requires = [
         'dbus-python',
+        'systemd-python',
         'Jinja2>=2.10',
         'PyGObject',
         'sonic-py-common'