Add --failfast option when running unit tests

tox.ini

@@ -21,7 +21,7 @@ deps =
     yourdfpy >=0.0.56
 commands =
     coverage erase
-    coverage run -m unittest tests
+    coverage run -m unittest tests --failfast
     coverage report --include="robot_descriptions/**"
 
 [testenv:lint]
@@ -50,37 +50,37 @@ changedir = {toxinidir}/tests/loaders
 deps =
     idyntree >= 8.0.0
 commands =
-    python -m unittest test_idyntree.py
+    python -m unittest test_idyntree.py --failfast
 
 [testenv:loader-mujoco]
 changedir = {toxinidir}/tests/loaders
 deps =
     mujoco >=2.3.5
 commands =
-    python -m unittest test_mujoco.py
+    python -m unittest test_mujoco.py --failfast
 
 [testenv:loader-pinocchio]
 changedir = {toxinidir}/tests/loaders
 deps =
     pin >=2.6.14
 commands =
-    python -m unittest test_pinocchio.py
+    python -m unittest test_pinocchio.py --failfast
 
 [testenv:loader-pybullet]
 changedir = {toxinidir}/tests/loaders
 deps =
     numpy >=1.23.4,<2
     pybullet >=3.2.5
 commands =
-    python -m unittest test_pybullet.py
+    python -m unittest test_pybullet.py --failfast
 
 [testenv:loader-robomeshcat]
 changedir = {toxinidir}/tests/loaders
 deps =
     pycollada >=0.6
     robomeshcat >= 1.0.4
 commands =
-    python -m unittest test_robomeshcat.py
+    python -m unittest test_robomeshcat.py --failfast
 
 [testenv:loader-yourdfpy]
 changedir = {toxinidir}/tests/loaders
@@ -90,7 +90,7 @@ deps =
     trimesh ~=3.16.0
     yourdfpy >=0.0.56
 commands =
-    python -m unittest test_yourdfpy.py
+    python -m unittest test_yourdfpy.py --failfast
 
 [pylint]
 generated-members=mujoco.MjModel, pin.JointModelFreeFlyer, pin.JointModelPX, pin.JointModelPY, pin.JointModelPZ, pin.JointModelPlanar, pin.JointModelRX, pin.JointModelRY, pin.JointModelRZ, pin.JointModelSpherical, pin.JointModelSphericalZYX, pin.JointModelTranslation, pin.Model, pybullet.loadURDF, pybullet.setAdditionalSearchPath