Add a DisjunctionError exception and use it

in case there is no possible disjoint path with the added constraints
(most of the time due to an inconsistant user request)

Signed-off-by: EstherLerouzic <esther.lerouzic@orange.com>

examples/path_requests_run.py

@@ -436,7 +436,11 @@ def main(args):
     print(rqs)
 
     print('\x1b[1;34;40m' + f'Computing all paths with constraints' + '\x1b[0m')
-    pths = compute_path_dsjctn(network, equipment, rqs, dsjn)
+    try:
+        pths = compute_path_dsjctn(network, equipment, rqs, dsjn)
+    except DisjunctionError as this_e:
+        print(f'{ansi_escapes.red}Disjunction error:{ansi_escapes.reset} {this_e}')
+        exit(1)
 
     print('\x1b[1;34;40m' + f'Propagating on selected path' + '\x1b[0m')
     propagatedpths, reversed_pths, reversed_propagatedpths = \

gnpy/core/exceptions.py

@@ -21,3 +21,5 @@ class NetworkTopologyError(ConfigurationError):
 class ServiceError(Exception):
     '''Service of user-provided request is wrong'''
 
+class DisjunctionError(ServiceError):
+    '''Disjunction of user-provided request can not be satisfied'''

gnpy/core/request.py

@@ -24,7 +24,7 @@ from gnpy.core.service_sheet import convert_service_sheet, Request_element, Elem
 from gnpy.core.elements import Transceiver, Roadm, Edfa, Fused
 from gnpy.core.utils import db2lin, lin2db
 from gnpy.core.info import create_input_spectral_information, SpectralInformation, Channel, Power
-from gnpy.core.exceptions import ServiceError
+from gnpy.core.exceptions import ServiceError, DisjunctionError
 from copy import copy, deepcopy
 from csv import writer
 from math import ceil
@@ -878,7 +878,7 @@ def compute_path_dsjctn(network, equipment, pathreqlist, disjunctions_list):
                 LOGGER.critical(msg)
                 print(f'{msg}\nComputation stopped.')
                 # TODO in this case: replay step 5  with the candidate without constraints
-                exit()
+                raise DisjunctionError(msg)
 
     # for i in disjunctions_list:
     #     print(i.disjunction_id)