Deprecate Python 3.3 support, with the intention of being removed in the next release (#3566)

* Deprecate Python 3.3 support, with the intention of being removed in the next release

* whoops
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index c48b709..a1fdea7 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -13,6 +13,8 @@
   has always been to check whether or not
   :class:`~cryptography.exceptions.InvalidSignature` was raised.
 * **BACKWARDS INCOMPATIBLE:** Dropped support for macOS 10.7 and 10.8.
+* Python 3.3 support has been deprecated, and will be removed in the
+  ``cryptography`` release.
 * Add support for providing ``tag`` during
   :class:`~cryptography.hazmat.primitives.ciphers.modes.GCM` finalization via
   :meth:`~cryptography.hazmat.primitives.ciphers.AEADDecryptionContext.finalize_with_tag`.
diff --git a/docs/installation.rst b/docs/installation.rst
index 9ee966a..8acac2e 100644
--- a/docs/installation.rst
+++ b/docs/installation.rst
@@ -24,6 +24,8 @@
     Python 2.6 is no longer supported by the Python core team. A future version
     of cryptography will drop support for this version.
 
+    Python 3.3 support will be removed in the next cryptography release.
+
 We test compiling with ``clang`` as well as ``gcc`` and use the following
 OpenSSL releases:
 
diff --git a/src/cryptography/__init__.py b/src/cryptography/__init__.py
index 940c66b..a0c8d46 100644
--- a/src/cryptography/__init__.py
+++ b/src/cryptography/__init__.py
@@ -25,3 +25,9 @@
         "support for Python 2.6",
         DeprecationWarning
     )
+if sys.version_info[:2] == (3, 3):
+    warnings.warn(
+        "Python 3.3 support will be dropped in the next release of"
+        "cryptography. Please upgrade your Python.",
+        DeprecationWarning,
+    )