upgrading delegator.py to resolve PYTHONUNBUFFERED issue in shell

Pipfile

@@ -2,7 +2,7 @@
 flake8 = ">=3.3.0,<4"
 pytest = "*"
 mock = "*"
-"delegator.py" = ">=0.0.12"
+"delegator.py" = ">=0.0.13"
 toml = "*"
 Sphinx = "<=1.5.5"
 

pipenv/vendor/delegator.py

@@ -5,9 +5,6 @@ import signal
 
 from pexpect.popen_spawn import PopenSpawn
 
-# Enable Python subprocesses to work with expect functionality.
-os.environ['PYTHONUNBUFFERED'] = '1'
-
 # Include `unicode` in STR_TYPES for Python 2.X
 try:
     STR_TYPES = (str, unicode)
@@ -147,6 +144,8 @@ class Command(object):
             pexpect_kwargs = self._default_pexpect_kwargs.copy()
             if binary:
                 pexpect_kwargs['encoding'] = None
+            # Enable Python subprocesses to work with expect functionality.
+            pexpect_kwargs['env']['PYTHONUNBUFFERED'] = '1'
             s = PopenSpawn(self._popen_args, **pexpect_kwargs)
         self.subprocess = s
         self.was_run = True
@@ -260,4 +259,4 @@ def run(command, block=True, binary=False, timeout=TIMEOUT):
     if block:
         c.block()
 
-    return c
+    return c