Upgrade to isort 4.3.4.

3rdparty/python/requirements.txt

@@ -9,7 +9,6 @@ fasteners==0.14.1
 faulthandler==2.6
 future==0.16.0
 futures==3.0.5
-isort==4.2.5
 Markdown==2.1.1
 mock==2.0.0
 packaging==16.8

src/python/pants/backend/python/subsystems/isort.py

@@ -9,7 +9,7 @@
 
 class Isort(Script):
   options_scope = 'isort'
-  default_version = '4.2.5'
+  default_version = '4.3.4'
   suffix = '.pex'
 
   replaces_scope = 'fmt.isort'

src/python/pants/backend/python/tasks/python_isort.py

@@ -22,12 +22,6 @@
 class IsortPythonTask(FmtTaskMixin, Task):
   """Autoformats Python source files with isort.
 
-  isort binary is built at contrib/python/src/python/pants/contrib/python/isort,
-  then uploaded to
-  https://github.com/pantsbuild/binaries/tree/gh-pages/build-support/scripts
-
-  TODO: Explain why we don't invoke isort directly.
-
   Behavior:
   ./pants fmt.isort <targets> -- <args, e.g. "--recursive ."> will sort the files only related
     to specified targets, but the way of finding the config(s) is vanilla. If no target is
@@ -58,6 +52,8 @@ def execute(self, test_output_file=None):
     cmd = [isort_script] + self.get_passthru_args() + sources
     logging.debug(' '.join(cmd))
 
+    # NB: We execute isort out of process to avoid unwanted side-effects from importing it:
+    #   https://github.com/timothycrosley/isort/issues/456
     try:
       subprocess.check_call(cmd, cwd=get_buildroot(),
                             stderr=test_output_file, stdout=test_output_file)

src/python/pants/util/netrc.py

@@ -7,8 +7,8 @@
 import collections
 import os
 from builtins import object
-from netrc import netrc as NetrcDb
 from netrc import NetrcParseError
+from netrc import netrc as NetrcDb
 
 
 class Netrc(object):