tests: Drop hypothesis from the tests.

Hypothesis recently had some problems with the typing module breaking
the tox tests.

Since Hypothesis isn't really used much in the test this patch removes
it from them as well as from the test-requirements.

python/test-requirements.txt

 pytest
-hypothesis
 pytest-flake8
 pytest-isort
 pytest-cov

python/tests/account_test.py

 from builtins import int
 
 import pytest
-from hypothesis import given
-from hypothesis.strategies import text
 
 from olm import Account, OlmAccountError, OlmVerifyError, ed25519_verify
 from olm._compat import to_bytes
@@ -73,8 +71,8 @@ class TestClass(object):
         alice = Account()
         del alice
 
-    @given(text())
-    def test_valid_signature(self, message):
+    def test_valid_signature(self):
+        message = "It's a secret to everybody"
         alice = Account()
 
         signature = alice.sign(message)
@@ -85,8 +83,8 @@ class TestClass(object):
 
         ed25519_verify(signing_key, message, signature)
 
-    @given(text())
-    def test_invalid_signature(self, message):
+    def test_invalid_signature(self):
+        message = "It's a secret to everybody"
         alice = Account()
         bob = Account()
 
@@ -99,8 +97,8 @@ class TestClass(object):
         with pytest.raises(OlmVerifyError):
             ed25519_verify(signing_key, message, signature)
 
-    @given(text())
-    def test_signature_verification_twice(self, message):
+    def test_signature_verification_twice(self):
+        message = "It's a secret to everybody"
         alice = Account()
 
         signature = alice.sign(message)

python/tests/utils_test.py

@@ -2,16 +2,16 @@ import base64
 import hashlib
 
 from future.utils import bytes_to_native_str
-from hypothesis import given
-from hypothesis.strategies import text
 
 from olm import sha256
 from olm._compat import to_bytes
 
 
 class TestClass(object):
-    @given(text(), text())
-    def test_sha256(self, input1, input2):
+    def test_sha256(self):
+        input1 = "It's a secret to everybody"
+        input2 = "It's a secret to nobody"
+
         first_hash = sha256(input1)
         second_hash = sha256(input2)