Denylist ecdsa 0.15 in setup.py to allow for 0.16 to be installed.

The previous pull request #192 only changed the pin in requirements.txt and not in setup.py, so the ecdsa<0.15 restriction would actually be used by pip.

Author: dreid

setup.py

@@ -38,7 +38,7 @@ def _cryptography_version():
     'pycrypto': ['pycrypto >=2.6.0, <2.7.0'] + pyasn1,
     'pycryptodome': ['pycryptodome >=3.3.1, <4.0.0'] + pyasn1,
 }
-legacy_backend_requires = ['ecdsa <0.15', 'rsa'] + pyasn1
+legacy_backend_requires = ['ecdsa != 0.15', 'rsa'] + pyasn1
 install_requires = ['six <2.0']
 
 # TODO: work this into the extras selection instead.
@@ -78,7 +78,7 @@ def _cryptography_version():
     ],
     tests_require=[
         'six',
-        'ecdsa<0.15',
+        'ecdsa != 0.15',
         'pytest',
         'pytest-cov',
         'pytest-runner',