diff --git a/README.md b/README.md
index cc8b678..b8f037c 100644
--- a/README.md
+++ b/README.md
@@ -4,10 +4,12 @@
 
 ``check_omd`` is a Nagios / Icinga plugin for checking a particular [OMD](http://www.omdistro.org) site's services.
 
-# Requirements
+## Requirements
+
 I successfully tested the plugin with OMD site versions 1.20 to 2.70. As the plugin needs to be executed **by the site user**, a sudo rule is needed. A template (*``check_omd-sudo-template``*) is part of the repository.
 
-# Usage
+## Usage
+
 By default, the script checks all services of the site - it is also possible to exclude services if they are predicted to fail in your environment (*``-x`` / ``--exclude`` parameters*).
 
 The following parameters can be specified:
@@ -22,33 +24,40 @@ The following parameters can be specified:
 | `--version` | prints programm version and quits |
 
 ## Examples
+
 The following example indicates an running OMD site:
-```
-$ ./check_omd.py 
+
+```shell
+$ ./check_omd.py
 OK: OMD site 'stankowic' services are running.
 ```
 
 A site with a failed ``nagios`` service:
-```
-$ ./check_omd.py 
+
+```shell
+$ ./check_omd.py
 CRITICAL: OMD site 'hansel' has failed service(s): 'nagios'
 ```
 
 OMD site ``giertz`` with a well-known daemon, that's crashing sometimes:
-```
+
+```shell
 $ ./check_omd.py -x npcd
 OK: OMD site 'giertz' services are running.
 ```
 
 OMD site ``clpmchn``, excluding npcd from throwing critical states:
-```
+
+```shell
 $ ./check_omd.py -w npcd
 WARNING: OMD site 'clpmchn' has service(s) in warning state: 'npcd'
 ```
 
-# Installation
+## Installation
+
 To install the plugin, move the Python script, the agent configuration and sudo rule into their appropriate directories. The paths may vary, depending on your Linux distribution and architecture. For RPM-based distribtions, proceed with the following steps:
-```
+
+```shell
 # mv check_omd.py /usr/lib64/nagios/plugins
 # mv check_omd-sudo-template /etc/sudoers.d/
 # chmod +x /usr/lib64/nagios/plugins/check_omd.py
@@ -56,33 +65,41 @@ To install the plugin, move the Python script, the agent configuration and sudo
 ```
 
 When using NRPE, copy the appropriate configuration and restart the daemon:
-```
+
+```shell
 # mv check_omd.cfg /etc/nrpe.d/
 # service nrpe restart
 ```
 
 When using Icinga2, copy the configuration to **ITL** (*Icinga Template Library*), e.g.:
-```
+
+```shell
 # cp check_omd.conf /usr/share/icinga2/include/plugins-contrib.d/
 # service icinga2 restart
 ```
 
 Make sure to alter the sudo configuration to match your OMD site name, e.g.:
-```
+
+```shell
 nrpe ALL = (stankowic) NOPASSWD: /usr/lib64/nagios/plugins/check_omd.py
 ```
 
 It also possible to create a RPM file for your Linux distribution with the RPM spec file:
-```
+
+```shell
 $ rpmbuild -ba nagios-plugins-check_omd.spec
+...
 ```
+
 The RPM spec has been tested on Enterprise Linux 5 to 7, i386 and x86_64. Currently, the RPM package only includes NRPE-related configuration, Icinga2 will follow.
 
-# Configuration
+## Configuration
+
+### Nagios / Icinga 1.x
 
-## Nagios / Icinga 1.x
 Inside Nagios / Icinga you will need to configure a remote check command, e.g. for NRPE:
-```
+
+```text
 #check_nrpe_omd
 define command{
     command_name        check_nrpe_omd
@@ -91,7 +108,8 @@ define command{
 ```
 
 Configure the check for a particular host, e.g.:
-```
+
+```text
 #SRV: omd stankowic
 define service{
         use                             generic-service
@@ -101,9 +119,11 @@ define service{
 }
 ```
 
-## Icinga2
+### Icinga2
+
 Define a service like this:
-```
+
+```text
 apply Service for (SITE => config in host.vars.omd_sites) {
   import "generic-service"
   check_command = "check_omd"
@@ -117,7 +137,8 @@ apply Service for (SITE => config in host.vars.omd_sites) {
 ```
 
 Create ``omd_site`` dictionaries for your hosts and assign the ``app`` variable:
-```
+
+```text
 object Host "st-mon04.stankowic.loc" {
   import "linux-host"
   ...
@@ -132,23 +153,28 @@ object Host "st-mon04.stankowic.loc" {
 ```
 
 Validate the configuration and reload the Icinga2 daemon:
-```
+
+```shell
 # icinga2 daemon -C
 # service icinga2 reload
 ```
 
-# Troubleshooting
-## Plugin not executed as OMD site user
+## Troubleshooting
+
+### Plugin not executed as OMD site user
+
 The plugin will not work if is not executed as site user:
-```
+
+```shell
 $ whoami
 taylor
-$ ./check_omd.py 
+$ ./check_omd.py
 UNKNOWN: unable to check site: 'omd: no such site: taylor' - did you miss running this plugin as OMD site user?
 ```
 
-An error message like this will be displayed if multiple OMD sites are available and you're running the plugin as root:
-```
+An error message like this will be displayed if multiple OMD sites are available and you're running the plugin as `root`:
+
+```shell
 # ./check_omd.py
 UNKOWN: unable to check site, it seems this plugin is executed as root (use OMD site context!)
 ````
diff --git a/check_omd.py b/check_omd.py
index d9083e0..662285d 100755
--- a/check_omd.py
+++ b/check_omd.py
@@ -13,6 +13,7 @@
 from optparse import OptionParser
 import subprocess
 import io
+import sys
 import logging
 
 __version__ = "1.1.1"
@@ -50,13 +51,13 @@ def get_site_status():
                 "running this plugin as OMD site user?".format(err.rstrip()))
         else:
             print("UNKNOWN: unable to check site: '{0}'".format(err.rstrip()))
-        exit(3)
+        sys.exit(3)
     if res:
         #try to find out whether omd was executed as root
         if res.count(bytes("OVERALL", "utf-8")) > 1:
             print("UNKOWN: unable to check site, it seems this plugin is " \
                 "executed as root (use OMD site context!)")
-            exit(3)
+            sys.exit(3)
 
         #check all services
         fail_srvs = []
@@ -80,7 +81,12 @@ def get_site_status():
                         if OPTIONS.heal:
                             cmd = ['omd', 'restart', service]
                             LOGGER.debug("running command '%s'", cmd)
-                            proc = subprocess.Popen(cmd, stderr=subprocess.PIPE, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
+                            proc = subprocess.Popen(
+                                cmd,
+                                stderr=subprocess.PIPE,
+                                stdin=subprocess.PIPE,
+                                stdout=subprocess.PIPE
+                            )
                             res2, err2 = proc.communicate()
                             print("{}".format(res2.rstrip().decode("utf-8")))
                             restarted_srvs.append(service)
@@ -96,21 +102,25 @@ def get_site_status():
                 )
         if OPTIONS.heal:
             if len(restarted_srvs) > 0:
-                print("WARNING: Restarted services on site '{0}': '{1}'".format(site, ' '.join(restarted_srvs)))
-                exit(1)
+                print(
+                    "WARNING: Restarted services on site '{0}': '{1}'".format(
+                        site, ' '.join(restarted_srvs)
+                    )
+                )
+                sys.exit(1)
             else:
-                exit(0)
+                sys.exit(0)
         if len(fail_srvs) == 0 and len(warn_srvs) == 0:
             print("OK: OMD site '{0}' services are running.".format(site))
-            exit(0)
+            sys.exit(0)
         elif len(fail_srvs) > 0:
             print("CRITICAL: OMD site '{0}' has failed service(s): " \
                 "'{1}'".format(site, ' '.join(fail_srvs)))
-            exit(2)
+            sys.exit(2)
         else:
             print("WARNING: OMD site '{0}' has service(s) in warning state: " \
                 "'{1}'".format(site, ' '.join(warn_srvs)))
-            exit(1)
+            sys.exit(1)
 
 
 
diff --git a/test/README.md b/test/README.md
index d4bfc8f..b4e97fc 100644
--- a/test/README.md
+++ b/test/README.md
@@ -16,6 +16,7 @@ Open a shell, move to this folder an run the following command to create the tes
 
 ```shell
 $ vagrant up
+...
 ```
 
 This will take a couple of minutes, as a CentOS 7 template is downloaded and deployed. It will also automatically install and configure OMD.
@@ -25,4 +26,6 @@ Afterwards, create a SSH configuration and run the tests using `pytest`:
 ```shell
 $ vagrant ssh-config > .vagrant/ssh_config
 $ py.test --connection=ssh --ssh-config .vagrant/ssh_config --hosts=omd test_plugin.py --sudo
+...
+=== 3 passed in 4.01s ===
 ```
diff --git a/test/test_plugin.py b/test/test_plugin.py
index bbc3e94..0be9c32 100644
--- a/test/test_plugin.py
+++ b/test/test_plugin.py
@@ -1,7 +1,7 @@
 """
 Plugin unit tests
 """
-import os
+
 
 def test_exclude(host):
     """