Unable to update "Subversion HTTP Server URL" field in admin settings

While configuring the admin settings, I entered “Subversion HTTP Server URL” as “”. But after sometime found that this field should be configured as “http://localhost:8090”. So now I updated this value in the input field and clicked “Generate apache config”. As soon as I click that button, a green banner says that update is done successully. But when I check this again, it was not saved, so when I looked at the logs I found some permission error like this

2018-06-08 16:31:56.457 [24896] ERROR [rhodecode.subscribers] Exception while executing command ['/etc/apache2', 'reload'].
Traceback (most recent call last):
  File "/opt/rhodecode/store/bbjmr1bwgmqsdkajzkmm5hk16al1b3ag-python2.7-rhodecode-enterprise-ce-4.12.2/lib/python2.7/site-packages/rhodecode/subscribers.py", line 308, in run
cmd, timeout=timeout, stderr=subprocess32.STDOUT)
  File "/opt/rhodecode/store/8sfz8gapjhkwnvva07mrw8ibinp0085y-python2.7-subprocess32-3.2.7/lib/python2.7/site-packages/subprocess32.py", line 629, in check_output
process = Popen(stdout=PIPE, *popenargs, **kwargs)
  File "/opt/rhodecode/store/8sfz8gapjhkwnvva07mrw8ibinp0085y-python2.7-subprocess32-3.2.7/lib/python2.7/site-packages/subprocess32.py", line 825, in __init__
restore_signals, start_new_session)
  File "/opt/rhodecode/store/8sfz8gapjhkwnvva07mrw8ibinp0085y-python2.7-subprocess32-3.2.7/lib/python2.7/site-packages/subprocess32.py", line 1574, in _execute_child
    raise child_exception_type(errno_num, err_msg)
OSError: [Errno 13] Permission denied

To solve this, as specified in the documents rhodecode user , I tried to set apache run username as ‘rhodecode’ but that fails and I get an error like “Bad user rhodecode”. How can I solve this anyone help me?

Until now, I am able to do all other actions like adding repo, users, groups, etc no problem there but I am unable to checkout a repo successfully!!!