ModuleNotFoundError is generated when installaing custom app

Installing library_mangement…
Traceback (most recent call last):
File “/usr/lib/python3.6/runpy.py”, line 193, in _run_module_as_main
main”, mod_spec)
File “/usr/lib/python3.6/runpy.py”, line 85, in _run_code
exec(code, run_globals)
File “/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py”, line 99, in
main()
File “/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py”, line 18, in main
click.Group(commands=commands)(prog_name=‘bench’)
File “/home/frappe/frappe-bench/env/lib/python3.6/site-packages/click/core.py”, line 764, in call
return self.main(*args, **kwargs)
File “/home/frappe/frappe-bench/env/lib/python3.6/site-packages/click/core.py”, line 717, in main
rv = self.invoke(ctx)
File “/home/frappe/frappe-bench/env/lib/python3.6/site-packages/click/core.py”, line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File “/home/frappe/frappe-bench/env/lib/python3.6/site-packages/click/core.py”, line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File “/home/frappe/frappe-bench/env/lib/python3.6/site-packages/click/core.py”, line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File “/home/frappe/frappe-bench/env/lib/python3.6/site-packages/click/core.py”, line 555, in invoke
return callback(*args, **kwargs)
File “/home/frappe/frappe-bench/env/lib/python3.6/site-packages/click/decorators.py”, line 17, in new_func
return f(get_current_context(), *args, **kwargs)
File “/home/frappe/frappe-bench/apps/frappe/frappe/commands/init.py”, line 26, in _func
ret = f(frappe._dict(ctx.obj), *args, **kwargs)
File “/home/frappe/frappe-bench/apps/frappe/frappe/commands/site.py”, line 203, in install_app
_install_app(app, verbose=context.verbose)
File “/home/frappe/frappe-bench/apps/frappe/frappe/installer.py”, line 83, in install_app
sync_for(name, force=True, sync_everything=True, verbose=verbose, reset_permissions=True)
File “/home/frappe/frappe-bench/apps/frappe/frappe/model/sync.py”, line 49, in sync_for
folder = os.path.dirname(frappe.get_module(app_name + “.” + module_name).file)
File “/home/frappe/frappe-bench/apps/frappe/frappe/init.py”, line 826, in get_module
return importlib.import_module(modulename)
File “/home/frappe/frappe-bench/env/lib/python3.6/importlib/init.py”, line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File “”, line 994, in _gcd_import
File “”, line 971, in _find_and_load
File “”, line 953, in _find_and_load_unlocked
ModuleNotFoundError: No module named ‘library_mangement.library_management_system’