Log Message:
py-cryptography[_vectors]: updated to 2.6.1

2.6.1:
* Resolved an error in our build infrastructure that broke our Python3 wheels
  for macOS and Linux.

2.6:
* **BACKWARDS INCOMPATIBLE:** Removed
  cryptography.hazmat.primitives.asymmetric.utils.encode_rfc6979_signature
  and
  cryptography.hazmat.primitives.asymmetric.utils.decode_rfc6979_signature,
  which had been deprecated for nearly 4 years. Use
  :func:~cryptography.hazmat.primitives.asymmetric.utils.encode_dss_signature
  and
  :func:~cryptography.hazmat.primitives.asymmetric.utils.decode_dss_signature
  instead.
* **BACKWARDS INCOMPATIBLE**: Removed cryptography.x509.Certificate.serial,
  which had been deprecated for nearly 3 years. Use
  :attr:~cryptography.x509.Certificate.serial_number instead.
* Updated Windows, macOS, and manylinux1 wheels to be compiled with
  OpenSSL 1.1.1b.
* Added support for :doc:/hazmat/primitives/asymmetric/ed448 when using
  OpenSSL 1.1.1b or newer.
* Added support for :doc:/hazmat/primitives/asymmetric/ed25519 when using
  OpenSSL 1.1.1b or newer.
* :func:~cryptography.hazmat.primitives.serialization.load_ssh_public_key can
  now load ed25519 public keys.
* Add support for easily mapping an object identifier to its elliptic curve
  class via
  :func:~cryptography.hazmat.primitives.asymmetric.ec.get_curve_for_oid.
* Add support for OpenSSL when compiled with the no-engine
  (OPENSSL_NO_ENGINE) flag.