Fix tests for latest ASE (#381)

* Try latest ASE

Just to see if ASE fixes its bug

* fix

ci/install_dependencies.sh

@@ -2,5 +2,4 @@
 
 python -m pip install --upgrade pip
 pip install --pre torch torchvision -f https://download.pytorch.org/whl/nightly/cpu/torch_nightly.html
-pip install tqdm pyyaml future pkbar
-pip install 'ase<=3.17'
+pip install tqdm pyyaml future pkbar ase

tests/test_structure_optim.py

@@ -5,6 +5,7 @@ import torchani
 import copy
 import pickle
 from ase.optimize import BFGS
+from ase import Atoms
 
 
 path = os.path.dirname(os.path.realpath(__file__))
@@ -24,6 +25,9 @@ class TestStructureOptimization(unittest.TestCase):
         with open(datafile, 'rb') as f:
             all_atoms = pickle.load(f)
             for atoms in all_atoms:
+                # reconstructing Atoms object.
+                # ASE does not support loading pickled object from older version
+                atoms = Atoms(atoms.get_chemical_symbols(), positions=atoms.get_positions())
                 old_coordinates = copy.deepcopy(atoms.get_positions())
                 old_coordinates = torch.from_numpy(old_coordinates)
                 atoms.set_calculator(self.calculator)