Fix the issue where Import/Export was failing in linux runtime. Fixes #2166

Issue:
Changes done by Ashesh in pgAdmin4.py file for setting up PYTHONHOME variable to sys.prefix was applicable only for windows only.

Additionally I have also added exception handling for file provided by user for Backup/Restore/Import/Export.

web/pgadmin/tools/backup/__init__.py

@@ -226,7 +226,10 @@ def create_backup_job(sid):
     else:
         data = json.loads(request.data, encoding='utf-8')
 
-    backup_file = filename_with_file_manager_path(data['file'])
+    try:
+        backup_file = filename_with_file_manager_path(data['file'])
+    except Exception as e:
+        return bad_request(errormsg=str(e))
 
     # Fetch the server details like hostname, port, roles etc
     server = Server.query.filter_by(
@@ -324,7 +327,10 @@ def create_backup_objects_job(sid):
     else:
         data = json.loads(request.data, encoding='utf-8')
 
-    backup_file = filename_with_file_manager_path(data['file'])
+    try:
+        backup_file = filename_with_file_manager_path(data['file'])
+    except Exception as e:
+        return bad_request(errormsg=str(e))
 
     # Fetch the server details like hostname, port, roles etc
     server = Server.query.filter_by(

web/pgadmin/tools/import_export/__init__.py

@@ -223,7 +223,11 @@ def create_import_export_job(sid):
     storage_dir = get_storage_directory()
 
     if 'filename' in data:
-        _file = filename_with_file_manager_path(data['filename'], data['is_import'])
+        try:
+            _file = filename_with_file_manager_path(data['filename'], data['is_import'])
+        except Exception as e:
+            return bad_request(errormsg=str(e))
+
         if not _file:
             return bad_request(errormsg=_('Please specify a valid file'))
 

web/pgadmin/tools/restore/__init__.py

@@ -179,7 +179,10 @@ def create_restore_job(sid):
     else:
         data = json.loads(request.data, encoding='utf-8')
 
-    _file = filename_with_file_manager_path(data['file'])
+    try:
+        _file = filename_with_file_manager_path(data['file'])
+    except Exception as e:
+        return bad_request(errormsg=str(e))
 
     if _file is None:
         return make_json_response(