Error while installing erpnext int site

Hi,
while I am trying to install erpnext into site I am getting an error can any one please help me how to resolve

hlt@hlt-Satellite-C640:~/frappe-bench$ bench --site site3.local install-app erpnext 
/usr/local/lib/python2.7/dist-packages/cryptography/hazmat/primitives/constant_time.py:26: CryptographyDeprecationWarning: Support for your Python version is deprecated. The next version of cryptography will remove support. Please upgrade to a 2.7.x release that supports hmac.compare_digest as soon as possible.
  utils.DeprecatedIn23,

Installing erpnext...
Traceback (most recent call last):
  File "/home/hlt/frappe-bench/apps/frappe/frappe/model/base_document.py", line 312, in db_insert
    ), list(d.values()))
  File "/home/hlt/frappe-bench/apps/frappe/frappe/database.py", line 199, in sql
    self._cursor.execute(query, values)
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/pymysql/cursors.py", line 170, in execute
    result = self._query(query)
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/pymysql/cursors.py", line 328, in _query
    conn.query(q)
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/pymysql/connections.py", line 516, in query
    self._affected_rows = self._read_query_result(unbuffered=unbuffered)
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/pymysql/connections.py", line 727, in _read_query_result
    result.read()
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/pymysql/connections.py", line 1066, in read
    first_packet = self.connection._read_packet()
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/pymysql/connections.py", line 683, in _read_packet
    packet.check_error()
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/pymysql/protocol.py", line 220, in check_error
    err.raise_mysql_exception(self._data)
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/pymysql/err.py", line 109, in raise_mysql_exception
    raise errorclass(errno, errval)
pymysql.err.IntegrityError: (1062, "Duplicate entry 'Accounts' for key 'PRIMARY'")

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.4/runpy.py", line 170, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.4/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/hlt/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 97, in <module>
    main()
  File "/home/hlt/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 18, in main
    click.Group(commands=commands)(prog_name='bench')
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/home/hlt/frappe-bench/env/lib/python3.4/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/hlt/frappe-bench/apps/frappe/frappe/commands/__init__.py", line 25, in _func
    ret = f(frappe._dict(ctx.obj), *args, **kwargs)
  File "/home/hlt/frappe-bench/apps/frappe/frappe/commands/site.py", line 165, in install_app
    _install_app(app, verbose=context.verbose)
  File "/home/hlt/frappe-bench/apps/frappe/frappe/installer.py", line 143, in install_app
    add_module_defs(name)
  File "/home/hlt/frappe-bench/apps/frappe/frappe/installer.py", line 342, in add_module_defs
    d.save(ignore_permissions=True)
  File "/home/hlt/frappe-bench/apps/frappe/frappe/model/document.py", line 260, in save
    return self._save(*args, **kwargs)
  File "/home/hlt/frappe-bench/apps/frappe/frappe/model/document.py", line 283, in _save
    self.insert()
  File "/home/hlt/frappe-bench/apps/frappe/frappe/model/document.py", line 237, in insert
    raise e
  File "/home/hlt/frappe-bench/apps/frappe/frappe/model/document.py", line 234, in insert
    self.db_insert()
  File "/home/hlt/frappe-bench/apps/frappe/frappe/model/base_document.py", line 323, in db_insert
    raise frappe.DuplicateEntryError(self.doctype, self.name, e)
frappe.exceptions.DuplicateEntryError: ('Module Def', 'Accounts', IntegrityError(1062, "Duplicate entry 'Accounts' for key 'PRIMARY'"))
hlt@hlt-Satellite-C640:~/frappe-bench$

First of all @anil4b6, the version of Python you are using could be an issue. Check the prerequisite requirements here.

As the first warning on your log…

CryptographyDeprecationWarning: Support for your Python version is deprecated. The next version of cryptography will remove support. Please upgrade to a 2.7.x release that supports hmac.compare_digest as soon as possible.
utils.DeprecatedIn23,

Another question:
Are you doing the installation on a fresh server?

Regards…

Try this:
bench --site site3.local reinstall