fix: Fix stringifying λ environment variables when using Python2 (aws…

…#579)

samcli/local/lambdafn/env_vars.py

@@ -2,6 +2,8 @@
 Supplies the environment variables necessary to set up Local Lambda runtime
 """
 
+import sys
+
 
 class EnvironmentVariables(object):
     """
@@ -191,7 +193,12 @@ def _stringify_value(self, value):
             result = "false"
 
         # value is a scalar type like int, str which can be stringified
-        else:
+        # do not stringify unicode in Py2, Py3 str supports unicode
+        elif sys.version_info.major > 2:
             result = str(value)
+        elif not isinstance(value, unicode):  # noqa: F821 pylint: disable=undefined-variable
+            result = str(value)
+        else:
+            result = value
 
         return result

tests/unit/local/lambdafn/test_env_vars.py

@@ -325,6 +325,7 @@ def test_must_replace_non_scalar_with_blank_values(self, input):
         (False, "false"),
         (1234, "1234"),
         (3.14, "3.14"),
+        (u"mystring\xe0", u"mystring\xe0"),
         ("mystring", "mystring"),
     ])
     def test_must_stringify(self, input, expected):