make SchedResourceList optional in flux.job.info

Problem: We currently cannot package rlist.h with the install (at
least without more work) and since this is a required import for
flux.job.info, without it the Python bindings (installed via pip)
will error.
Solution: the flux.resource module is not technically required,
so we can fallback to catching the ImportError instead and using
the same empty (dummy) class to handle self.resources

Signed-off-by: vsoch <vsoch@users.noreply.github.com>

src/bindings/python/flux/job/info.py

@@ -22,9 +22,13 @@
 from flux.job.JobID import JobID
 from flux.job.stats import JobStats
 from flux.memoized_property import memoized_property
-from flux.resource import SchedResourceList
 from flux.uri import JobURI
 
+try:
+    from flux.resource import SchedResourceList
+except ImportError:
+    SchedResourceList = None
+
 
 def statetostr(stateid, fmt="L"):
     return raw.flux_job_statetostr(stateid, fmt).decode("utf-8")
@@ -212,7 +216,7 @@ class InstanceInfo:
     def __init__(self, uri=None):
         self.initialized = False
         try:
-            if not uri:
+            if not uri or SchedResourceList is None:
                 raise ValueError
             handle = flux.Flux(str(uri))
             future = handle.rpc("sched.resource-status")