Fix docs-building on old stable branches

For a while now, the nightly job has bombed out with something like

   Warning, treated as error:
   .../swift/doc/source/middleware.rst:268: (WARNING/2) autodoc: failed to import module
   'swift.common.middleware.xprofile'; the following exception was raised:
   Traceback (most recent call last):
     File ".../python3.5/site-packages/sphinx/ext/autodoc.py", line 657, in import_object
       __import__(self.modname)
     File ".../python3.5/site-packages/swift/common/middleware/xprofile.py", line 82, in <module>
       import eventlet.green.profile as eprofile
     File ".../python3.5/site-packages/eventlet/green/profile.py", line 45, in <module>
       thread = patcher.original('thread')  # non-monkeypatched module needed
     File ".../python3.5/site-packages/eventlet/patcher.py", line 194, in original
       real_mod = __import__(modname, {}, {}, modname.split('.')[:-1])
   ImportError: No module named 'thread'

Not sure why we're running under py35 (the job definition calls out
`sphinx_python: python2`), but that's the crux of the issue -- neither
us nor our dependencies support py3 that far back, so having eventlet
constrained to 0.20.0 on stable/pike and stable/queens is setting us up
for failure.

On the plus side, it's just docs! We don't really *need* this import to
build docs, so catch the ImportError and call it None.

After that, also need to fix some import for xprofile.

Also, fix some tuple-unpacking-in-function-args trouble.

Related-Change: Ie8d28218b974a1b6b7b7b691f786ff1d6bdded05
Change-Id: I56f10d8e25e57da59f3da57fe797f615433d70a7

swift/common/middleware/slo.py

@@ -808,7 +808,8 @@ class SloGetContext(WSGIContext):
         plain_listing_iter = self._segment_listing_iterator(
             req, ver, account, segments, byteranges)
 
-        def is_small_segment((seg_dict, start_byte, end_byte)):
+        def is_small_segment(args):
+            seg_dict, start_byte, end_byte = args
             start = 0 if start_byte is None else start_byte
             end = int(seg_dict['bytes']) - 1 if end_byte is None else end_byte
             is_small = (end - start + 1) < self.slo.rate_limit_under_size

swift/common/middleware/x_profile/html_viewer.py

@@ -21,9 +21,10 @@ import string
 import tempfile
 
 from swift import gettext_ as _
-from exceptions import PLOTLIBNotInstalled, ODFLIBNotInstalled,\
-    NotFoundException, MethodNotAllowed, DataLoadFailure, ProfileException
-from profile_model import Stats2
+from swift.common.middleware.x_profile.exceptions import PLOTLIBNotInstalled,\
+    ODFLIBNotInstalled, NotFoundException, MethodNotAllowed, DataLoadFailure,\
+    ProfileException
+from swift.common.middleware.x_profile.profile_model import Stats2
 
 PLOTLIB_INSTALLED = True
 try:

swift/common/middleware/xprofile.py

@@ -79,17 +79,23 @@ import sys
 import time
 
 from eventlet import greenthread, GreenPool, patcher
-import eventlet.green.profile as eprofile
+try:
+    import eventlet.green.profile as eprofile
+except ImportError:
+    # This is specifically for docs-building on old stable branches which have
+    # eventlet constrained to a version that doesn't include
+    # https://github.com/eventlet/eventlet/commit/f81b135a
+    eprofile = None
 import six
 from six.moves import urllib
 
 from swift import gettext_ as _
 from swift.common.utils import get_logger, config_true_value
 from swift.common.swob import Request
-from x_profile.exceptions import NotFoundException, MethodNotAllowed,\
-    ProfileException
-from x_profile.html_viewer import HTMLViewer
-from x_profile.profile_model import ProfileLog
+from swift.common.middleware.x_profile.exceptions import NotFoundException, \
+    MethodNotAllowed, ProfileException
+from swift.common.middleware.x_profile.html_viewer import HTMLViewer
+from swift.common.middleware.x_profile.profile_model import ProfileLog
 
 
 DEFAULT_PROFILE_PREFIX = '/tmp/log/swift/profile/default.profile'
@@ -107,7 +113,10 @@ PROFILE_EXEC_LAZY = """
 app_iter_ = self.app(environ, start_response)
 """
 
-thread = patcher.original('thread')  # non-monkeypatched module needed
+if six.PY3:
+    thread = patcher.original('_thread')  # non-monkeypatched module needed
+else:
+    thread = patcher.original('thread')  # non-monkeypatched module needed
 
 
 # This monkey patch code fix the problem of eventlet profile tool