python: split flux.job module into multiple files

Problem: The Python 'flux.job' module is large (>1200 lines)
and thus getting difficult to read and/or modify. This module will
only get larger since there will certainly be more classes and
methods related to Flux jobs added to the Python API.

Split `src/bindings/python/flux/job.py` into multiple files, while
attempting to keep related code together without making any one component
too large.

For backwards compatibility, recreate the previous `flux.job` namespace
in the __init__.py in the new job directory.

src/bindings/python/flux/Makefile.am

@@ -5,7 +5,6 @@ nobase_fluxpy_PYTHON = \
 	rpc.py \
 	message.py \
 	constants.py \
-	job.py \
 	util.py \
 	future.py \
 	memoized_property.py \
@@ -14,7 +13,17 @@ nobase_fluxpy_PYTHON = \
 	core/watchers.py \
 	core/inner.py \
 	core/handle.py \
-	core/trampoline.py
+	core/trampoline.py \
+	job/__init__.py \
+	job/JobID.py \
+	job/Jobspec.py \
+	job/event.py \
+	job/kill.py \
+	job/kvs.py \
+	job/list.py \
+	job/submit.py \
+	job/wait.py \
+	job/wrapper.py
 
 if HAVE_FLUX_SECURITY
 nobase_fluxpy_PYTHON += security.py

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

@@ -0,0 +1,99 @@
+###############################################################
+# Copyright 2020 Lawrence Livermore National Security, LLC
+# (c.f. AUTHORS, NOTICE.LLNS, COPYING)
+#
+# This file is part of the Flux resource manager framework.
+# For details, see https://github.com/flux-framework.
+#
+# SPDX-License-Identifier: LGPL-3.0
+###############################################################
+
+from flux.job.wrapper import RAW
+from _flux._core import ffi
+
+
+def id_parse(jobid_str):
+    """
+    returns: An integer jobid
+    :rtype int
+    """
+    jobid = ffi.new("flux_jobid_t[1]")
+    RAW.id_parse(jobid_str, jobid)
+    return int(jobid[0])
+
+
+def id_encode(jobid, encoding="f58"):
+    """
+    returns: Jobid encoded in encoding
+    :rtype str
+    """
+    buflen = 128
+    buf = ffi.new("char[]", buflen)
+    RAW.id_encode(int(jobid), encoding, buf, buflen)
+    return ffi.string(buf, buflen).decode("utf-8")
+
+
+class JobID(int):
+    """Class used to represent a Flux JOBID
+
+    JobID is a subclass of `int`, so may be used in place of integer.
+    However, a JobID may be created from any valid RFC 19 FLUID
+    encoding, including:
+
+     - decimal integer (no prefix)
+     - hexidecimal integer (prefix 0x)
+     - dotted hex (dothex) (xxxx.xxxx.xxxx.xxxx)
+     - kvs dir (dotted hex with `job.` prefix)
+     - RFC19 F58: (Base58 encoding with prefix `ƒ` or `f`)
+
+    A JobID object also has properties for encoding a JOBID into each
+    of the above representations, e.g. jobid.f85, jobid.words, jobid.dothex...
+
+    """
+
+    def __new__(cls, value):
+        if isinstance(value, int):
+            jobid = value
+        else:
+            jobid = id_parse(value)
+        return super(cls, cls).__new__(cls, jobid)
+
+    def encode(self, encoding="dec"):
+        """Encode a JobID to alternate supported format"""
+        return id_encode(self, encoding)
+
+    @property
+    def dec(self):
+        """Return decimal integer representation of a JobID"""
+        return self.encode()
+
+    @property
+    def f58(self):
+        """Return RFC19 F58 representation of a JobID"""
+        return self.encode("f58")
+
+    @property
+    def hex(self):
+        """Return 0x-prefixed hexidecimal representation of a JobID"""
+        return self.encode("hex")
+
+    @property
+    def dothex(self):
+        """Return dotted hexidecimal representation of a JobID"""
+        return self.encode("dothex")
+
+    @property
+    def words(self):
+        """Return words (mnemonic) representation of a JobID"""
+        return self.encode("words")
+
+    @property
+    def kvs(self):
+        """Return KVS directory path of a JobID"""
+        return self.encode("kvs")
+
+    def __str__(self):
+        return self.encode("f58")
+
+    def __repr__(self):
+        return f"JobID({self.dec})"