Avoid 'module: command not found' error (#60)

That error only happens when the user's default shell is /bin/csh on one
HPC. This is one way to fix the problem; the other involves adding a
"#PBS -S /bin/bash" line to the PBS script.

uit/pbs_script.py

@@ -332,7 +332,9 @@ def render_modules_block(self):
         Returns:
             str: All module calls.
         """
-        opt_list = [self._create_block_header_string('Modules')]
+        opt_list = [self._create_block_header_string('Modules'),
+                    "# Avoid 'module: command not found' error when default shell is /bin/csh",
+                    "source ${MODULESHOME}/init/bash"]
         for path in self._module_use:
             opt_list.append(f'module use --append {path}')
         for key, value in self._modules.items():