Fix test_encryption_decryption

It is broken since 28cae607a4

python/README.rst

@@ -65,7 +65,7 @@ Afterwards ``which python`` tells you that it comes out of the "venv"
 directory that contains all python install artifacts. Let's first
 install test tools::
 
-    pip install pytest pytest-timeout pytest-rerunfailures requests
+    pip install pytest pytest-timeout requests
 
 then cargo-build and install the deltachat bindings::
 

python/tox.ini

@@ -16,10 +16,7 @@ passenv =
     DCC_PY_LIVECONFIG
 deps = 
     pytest
-    pytest-rerunfailures
-    pytest-timeout
-    pytest-xdist
-    auditwheel
+    pytest-faulthandler
     pdbpp
     requests
 
@@ -54,12 +51,11 @@ commands =
 
 
 [pytest]
-addopts = -v -rs --reruns 3 --reruns-delay 2
+addopts = -v -rs
 python_files = tests/test_*.py 
 norecursedirs = .tox 
 xfail_strict=true
-timeout = 60 
-timeout_method = thread
+timeout = 60
 
 [flake8]
 max-line-length = 120