Command "python egg_info" failed with error code 1 in /home/erpnext/frappe-bench/apps/frappe/

I was trying to install erpnext in my server.While running bench get-app frappe command I am getting the following error. My os centos. app frappe
Cloning into 'frappe'...
Username for '':
Password for '': 
remote: Counting objects: 136088, done.
remote: Compressing objects: 100% (28/28), done.
remote: Total 136088 (delta 30), reused 44 (delta 27)
Receiving objects: 100% (136088/136088), 111.20 MiB | 2.76 MiB/s, done.
Resolving deltas: 100% (103681/103681), done.
installing frappe frappe
Command "python egg_info" failed with error code 1 in /home/erpnext/frappe-bench/apps/frappe/
Traceback (most recent call last):
  File "/usr/bin/bench", line 11, in <module>
    load_entry_point('bench', 'console_scripts', 'bench')()
  File "/home/erpnext/bench-repo/bench/", line 40, in cli
  File "/usr/lib/python2.7/site-packages/click/", line 716, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/click/", line 696, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python2.7/site-packages/click/", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python2.7/site-packages/click/", line 889, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python2.7/site-packages/click/", line 534, in invoke
    return callback(*args, **kwargs)
  File "/home/erpnext/bench-repo/bench/commands/", line 30, in get_app
    get_app(git_url, branch=branch)
  File "/home/erpnext/bench-repo/bench/", line 73, in get_app
    install_app(app=app_name, bench_path=bench_path, verbose=verbose)
  File "/home/erpnext/bench-repo/bench/", line 103, in install_app
  File "/home/erpnext/bench-repo/bench/", line 127, in exec_cmd
    raise CommandFailedError(cmd)
bench.utils.CommandFailedError: ./env/bin/pip install -q  -e ./apps/frappe

please help me to fix this error.

In sites directory apps.txt file insert your app_name then save and close.then
./env/bin/pip install -q -e ./apps/frappe --no-cache-dir

@PrashantPatil thanks for the reply . but there is no app.txt file

What do you mean @PrashantPatil by app_name?