gw_data_find server and obtaining data from graceDB

This MR ports over the changes from !418 (merged) relating to the way data is pulled from graceDB. I incorporated @gregory.ashton's suggestion to try to access the data_find server directly in python, but kept the logger output for which bash command the user can run if this fails (which it will if they're submitting to condor) and they want to run on a cluster besides CIT.

bilby/gw/utils.py

@@ -443,7 +443,7 @@ def read_frame_file(file_name, start_time, end_time, channel=None, buffer_time=0
         return None
 
 
-def get_gracedb(gracedb, outdir, duration, calibration, detectors, query_types=None):
+def get_gracedb(gracedb, outdir, duration, calibration, detectors, query_types=None, server=None):
     candidate = gracedb_to_json(gracedb, outdir)
     trigger_time = candidate['gpstime']
     gps_start_time = trigger_time - duration
@@ -453,7 +453,7 @@ def get_gracedb(gracedb, outdir, duration, calibration, detectors, query_types=N
     for i, det in enumerate(detectors):
         output_cache_file = gw_data_find(
             det, gps_start_time, duration, calibration,
-            outdir=outdir, query_type=query_types[i])
+            outdir=outdir, query_type=query_types[i], server=server)
         cache_files.append(output_cache_file)
     return candidate, cache_files
 
@@ -476,7 +476,7 @@ def gracedb_to_json(gracedb, outdir=None):
     logger.info('Initialise client and attempt to download')
     try:
         client = GraceDb()
-    except FileNotFoundError:
+    except IOError:
         raise ValueError(
             'Failed to authenticate with gracedb: check your X509 '
             'certificate is accessible and valid')
@@ -499,7 +499,7 @@ def gracedb_to_json(gracedb, outdir=None):
 
 
 def gw_data_find(observatory, gps_start_time, duration, calibration,
-                 outdir='.', query_type=None):
+                 outdir='.', query_type=None, server=None):
     """ Builds a gw_data_find call and process output
 
     Parameters
@@ -542,6 +542,13 @@ def gw_data_find(observatory, gps_start_time, duration, calibration,
     output_cache_file = os.path.join(outdir, cache_file)
 
     gps_end_time = gps_start_time + duration
+    if server is None:
+        server = os.environ.get("LIGO_DATAFIND_SERVER")
+        if server is None:
+            logger.warning('No data_find server found, defaulting to CIT server. '
+                           'To run on other clusters, pass the output of '
+                           '`echo $LIGO_DATAFIND_SERVER`')
+            server = 'ldr.ldas.cit:80'
 
     cl_list = ['gw_data_find']
     cl_list.append('--observatory {}'.format(observatory_code))
@@ -549,6 +556,7 @@ def gw_data_find(observatory, gps_start_time, duration, calibration,
     cl_list.append('--gps-end-time {}'.format(int(np.ceil(gps_end_time))))
     cl_list.append('--type {}'.format(query_type))
     cl_list.append('--output {}'.format(output_cache_file))
+    cl_list.append('--server {}'.format(server))
     cl_list.append('--url-type file')
     cl_list.append('--lal-cache')
     cl = ' '.join(cl_list)