Revert custodian subprocess in Q-Chem (#1844)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/quacc/calculators/qchem/qchem.py

@@ -2,10 +2,14 @@
 
 from __future__ import annotations
 
+import inspect
+import sys
+from pathlib import Path
 from typing import TYPE_CHECKING
 
 from ase.calculators.calculator import FileIOCalculator
 
+from quacc.calculators.qchem import qchem_custodian
 from quacc.calculators.qchem.io import read_qchem, write_qchem
 from quacc.calculators.qchem.params import cleanup_attrs, make_qc_input
 from quacc.calculators.qchem.qchem_custodian import run_custodian
@@ -241,11 +245,14 @@ def __init__(
         # Set default params
         self._set_default_params()
 
+        # Get Q-Chem executable command
+        command = self._manage_environment()
+
         # Instantiate the calculator
         super().__init__(
             restart=None,
             label=None,
-            command="",
+            command=command,
             atoms=self.atoms,
             profile=None,
             **self.fileiocalculator_kwargs,
@@ -306,6 +313,19 @@ def read_results(self) -> None:
         self.results = results
         self.prev_orbital_coeffs = prev_orbital_coeffs
 
+    @staticmethod
+    def _manage_environment() -> str:
+        """
+        Return the command to run the Q-Chem calculator via Custodian.
+        Returns
+        -------
+        str
+            The command flag to run Q-Chem with Custodian.
+        """
+
+        qchem_custodian_script = Path(inspect.getfile(qchem_custodian)).resolve()
+        return f"{sys.executable} {qchem_custodian_script}"
+
     def _set_default_params(self) -> None:
         """
         Store the parameters that have been passed to the Q-Chem calculator in