Change test condition: TRAVIS => Linux platform

tests/test_interact.py

diff --git a/tests/test_interact.py b/tests/test_interact.py
index 865353b..76a071e 100755
--- a/tests/test_interact.py
+++ b/tests/test_interact.py
@@ -24,6 +24,7 @@
 
 import os
 import pexpect
+import platform
 import unittest
 import sys
 from . import PexpectTestCase
@@ -62,10 +63,12 @@
         p.sendcontrol(']')
         p.expect('29<STOP>')
         p.send('\x00')
-        if not os.environ.get('TRAVIS', None):
-            # on Travis-CI, we sometimes miss trailing stdout from the
-            # chain of child processes, not entirely sure why. So this
-            # is skipped on such systems.
+
+        if not platform.system() == 'Linux':
+            # on Linux, we sometimes miss trailing stdout from the
+            # chain of child processes through a subprocess call to
+            # interact() method.  This condition so far is only reproduced
+            # within these constraints so far, skipped for now.
             p.expect('0<STOP>')
             p.expect_exact('Escaped interact')
         p.expect(pexpect.EOF)
@@ -84,10 +87,11 @@
         p.expect('206<STOP>')    # [206, 146]
         p.expect('146<STOP>')
         p.send('\x00')
-        if not os.environ.get('TRAVIS', None):
-            # on Travis-CI, we sometimes miss trailing stdout from the
-            # chain of child processes, not entirely sure why. So this
-            # is skipped on such systems.
+        if not platform.system() == 'Linux':
+            # on Linux, we sometimes miss trailing stdout from the
+            # chain of child processes through a subprocess call to
+            # interact() method.  This condition so far is only reproduced
+            # within these constraints so far, skipped for now.
             p.expect('0<STOP>')
             p.expect_exact('Escaped interact')
         p.expect(pexpect.EOF)