Switch from pkg_resource, and added defaults for the executable.

mopac_step/mopac.py

@@ -5,12 +5,13 @@
 import calendar
 import configparser
 import datetime
+import importlib
 import logging
 import os
 import os.path
 from pathlib import Path
-import pkg_resources
 import pprint
+import shutil
 import string
 
 import molsystem
@@ -25,8 +26,8 @@
 printer = printing.getPrinter("mopac")
 
 # Add MOPAC's properties to the standard properties
-path = Path(pkg_resources.resource_filename(__name__, "data/"))
-csv_file = path / "properties.csv"
+resources = importlib.resources.files("mopac_step") / "data"
+csv_file = resources / "properties.csv"
 molsystem.add_properties_from_file(csv_file)
 
 
@@ -262,16 +263,36 @@ def run(self, printer=printer):
 
                 executor = self.flowchart.executor
 
-                # Read configuration file for MOPAC
-                ini_dir = Path(seamm_options["root"]).expanduser()
-                full_config = configparser.ConfigParser()
-                full_config.read(ini_dir / "mopac.ini")
+                # Read configuration file for MOPAC if it exists
                 executor_type = executor.name
+                full_config = configparser.ConfigParser()
+                ini_dir = Path(seamm_options["root"]).expanduser()
+                path = ini_dir / "mopac.ini"
+
+                if path.exists():
+                    full_config.read(ini_dir / "mopac.ini")
+
+                # If the section we need doesn't exists, get the default
+                if not path.exists() or executor_type not in full_config:
+                    resources = importlib.resources.files("mopac_step") / "data"
+                    ini_text = (resources / "mopac.ini").read_text()
+                    full_config.read_string(ini_text)
+
+                # Getting desperate! Look for an executable in the path
                 if executor_type not in full_config:
-                    raise RuntimeError(
-                        f"No section for '{executor_type}' in MOPAC ini file "
-                        f"({ini_dir / 'mopac.ini'})"
-                    )
+                    path = shutil.which("mopac")
+                    if path is None:
+                        raise RuntimeError(
+                            f"No section for '{executor_type}' in MOPAC ini file "
+                            f"({ini_dir / 'mopac.ini'}), nor in the defaults, nor "
+                            "in the path!"
+                        )
+                    else:
+                        full_config[executor_type] = {
+                            "installation": "local",
+                            "code": str(path)
+                        }
+
                 config = dict(full_config.items(executor_type))
 
                 return_files = [