diff -r 5673cf852daa Lib/netrc.py
--- a/Lib/netrc.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/netrc.py	Sun Oct 02 16:47:15 2016 +0200
@@ -23,10 +23,7 @@
     def __init__(self, file=None):
         default_netrc = file is None
         if file is None:
-            try:
-                file = os.path.join(os.environ['HOME'], ".netrc")
-            except KeyError:
-                raise OSError("Could not find .netrc: $HOME is not set")
+            file = os.path.expanduser("~/.netrc")
         self.hosts = {}
         self.macros = {}
         with open(file) as fp:
diff -r 5673cf852daa Lib/test/test_netrc.py
--- a/Lib/test/test_netrc.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_netrc.py	Sun Oct 02 16:47:15 2016 +0200
@@ -123,6 +123,11 @@
             os.chmod(fn, 0o622)
             self.assertRaises(netrc.NetrcParseError, netrc.netrc)
 
+    def test_no_home_in_env(self):
+        with support.EnvironmentVarGuard() as environ:
+            environ.unset('HOME')
+            nrc = netrc.netrc()
+
 def test_main():
     support.run_unittest(NetrcTestCase)