Fix tasks.py due to an Invoke breaking change

tasks.py

@@ -25,6 +25,11 @@ BASE = os.path.dirname(__file__)
 PYTHON = "python3"
 PROJECT = "managetests"
 
+# This is because invoke can't keep backward compatibility..
+_invoke_v = invoke.__version__.split(".")
+if int(_invoke_v[0]) == 0 and int(_invoke_v[1]) <= 12:
+    invoke.task = invoke.ctask
+
 
 def create_env(name, requirements=False, self=False, force=False):
     """Create a new virtual environment"""
@@ -47,13 +52,13 @@ def create_env(name, requirements=False, self=False, force=False):
 
 
 @invoke.task
-def devel():
+def devel(ctx):
     """Setup the development environment"""
     create_env("devel", self=True, force=True)
 
 
 @invoke.task
-def build():
+def build(ctx):
     """Create a new build"""
     env = create_env("build", requirements=True)
 
@@ -67,7 +72,7 @@ def build():
 
 
 @invoke.task
-def clean():
+def clean(ctx):
     """Clean all the build things"""
     for dir in "build", "%s.egg-info" % PROJECT:
         path = os.path.join(BASE, dir)