replace repeated string by const, in a few places

brian_polling_manager/eumetsat_multicast.py

 from brian_polling_manager import sensu
 
+_CHECK_PREFIX = 'eumetmc'
 
 def load_eumetsat_multicast_checks(sensu_params):
     def _is_eumetsat_multicast_check(check):
         name = check['metadata']['name']
-        return name.startswith('eumetmc')
+        return name.startswith(_CHECK_PREFIX)
     ifc_checks = filter(
         _is_eumetsat_multicast_check, sensu.load_all_checks(sensu_params))
     return {c['metadata']['name']: c for c in ifc_checks}
@@ -19,7 +20,7 @@ class EUMETSATMulticastHostCheck(sensu.AbstractCheck):
 
     @sensu.AbstractCheck.name.getter
     def name(self):
-        return f'eumetmc-{self.hostname}'
+        return f'{_CHECK_PREFIX}-{self.hostname}'
 
     @sensu.AbstractCheck.command.getter
     def command(self):

brian_polling_manager/gws_direct.py

 from brian_polling_manager import sensu
 
+_CHECK_PREFIX = 'gwsd'
+
 
 def load_gws_direct_checks(sensu_params):
     def _is_gws_direct_check(check):
         name = check['metadata']['name']
-        return name.startswith('gwsd')
+        return name.startswith(_CHECK_PREFIX)
     ifc_checks = filter(
         _is_gws_direct_check, sensu.load_all_checks(sensu_params))
     return {c['metadata']['name']: c for c in ifc_checks}
@@ -23,7 +25,7 @@ class GwSDirectInterfaceCheck(sensu.AbstractCheck):
         isp = isp.replace(' ', '_')
         tag = self.interface['tag']
         tag = tag.replace(' ', '_')
-        return f'gwsd-{self.interface["nren"]}-{isp}-{tag}'
+        return f'{_CHECK_PREFIX}-{self.interface["nren"]}-{isp}-{tag}'
 
     @sensu.AbstractCheck.command.getter
     def command(self):

brian_polling_manager/gws_indirect.py

 import re
 from brian_polling_manager import sensu
 
+_CHECK_PREFIX = 'dscp32'
+
 
 def load_dscp32_checks(sensu_params):
     def _is_dscp32_check(check):
         name = check['metadata']['name']
-        return name.startswith('dscp32')
+        return name.startswith(_CHECK_PREFIX)
     ifc_checks = filter(
         _is_dscp32_check, sensu.load_all_checks(sensu_params))
     return {c['metadata']['name']: c for c in ifc_checks}
@@ -21,7 +23,7 @@ class DSCP32CountersCheck(sensu.AbstractCheck):
     @sensu.AbstractCheck.name.getter
     def name(self):
         name = re.sub(r'[\s_-]+', '_', self.service['name'])
-        return f'dscp32-{name}'
+        return f'{_CHECK_PREFIX}-{name}'
 
     @sensu.AbstractCheck.command.getter
     def command(self):