Document UnsupportedAlgorithm in a super vague way.
diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
index 769ab98..1a2603b 100644
--- a/docs/hazmat/backends/interfaces.rst
+++ b/docs/hazmat/backends/interfaces.rst
@@ -334,6 +334,9 @@
             ``private_exponent``, ``public_exponent``, or ``modulus`` do not
             match the bounds specified in :rfc:`3447`.
 
+        :raises cryptography.exceptions.UnsupportedAlgorithm: This raised when
+            any backend specific criteria are not met.
+
     .. method:: load_rsa_public_numbers(numbers):
 
         :param numbers: An instance of
@@ -346,6 +349,9 @@
             ``public_exponent`` or ``modulus`` do not match the bounds
             specified in :rfc:`3447`.
 
+        :raises cryptography.exceptions.UnsupportedAlgorithm: This raised when
+            any backend specific criteria are not met.
+
 
 .. class:: TraditionalOpenSSLSerializationBackend