Revert "Add interpolate argument to avoid resolving proxied values."

This reverts commit 797101b.

docs/tips.rst

@@ -226,7 +226,7 @@ Proxy value
 ===========
 
 Values that being with a ``$`` may be interpolated. Pass ``interpolate=True`` to
-``environ.Env()`` to enable this feature (``True`` by default):
+``environ.Env()`` to enable this feature:
 
 .. code-block:: python
 

environ/environ.py

@@ -197,12 +197,11 @@ class Env:
     VAR = re.compile(r'(?<!\\)\$\{?(?P<name>[A-Z_][0-9A-Z_]*)}?',
                      re.IGNORECASE)
 
-    def __init__(self, interpolate=True, **scheme):
+    def __init__(self, **scheme):
         self._local = threading.local()
         self.smart_cast = True
         self.escape_proxy = False
         self.prefix = ""
-        self.interpolate = interpolate
         self.scheme = scheme
 
     def __call__(self, var, cast=None, default=NOTSET, parse_default=False):
@@ -426,8 +425,7 @@ def _get_value(self, var_name, cast=None, default=NOTSET,
             value = default
 
         # Expand variables
-        if self.interpolate and isinstance(value, (bytes, str)) \
-                and var_name not in NOT_EXPANDED:
+        if isinstance(value, (bytes, str)) and var_name not in NOT_EXPANDED:
             def repl(match_):
                 return self.get_value(
                     match_.group('name'), cast=cast, default=default,

tests/test_env.py

@@ -134,10 +134,6 @@ def test_bool_true(self, value, variable):
     def test_proxied_value(self):
         assert self.env('PROXIED_VAR') == 'bar'
 
-    def test_not_interpolated_proxied_value(self):
-        env = Env(interpolate=False)
-        assert env('PROXIED_VAR') == '$STR_VAR'
-
     def test_escaped_dollar_sign(self):
         self.env.escape_proxy = True
         assert self.env('ESCAPED_VAR') == '$baz'