Added Error handling for User errors

Some issues where raised where the users made an error when
executing pytm on the shell.

It seems that the issue is that pytm is not returning a custom error but
just a Python trace.

This commit add the UIError, which will be handled inside the process
function.

UIError is a warpper arround another exception and adds a context
description.

This commit only adds UIError for open calls in pytm, since these are
obvious pitfalls for users.

pytm/pytm.py

@@ -34,6 +34,12 @@
 """
 
 
+class UIError(Exception):
+    def __init__(self, e, context):
+        self.error = e
+        self.context = context
+
+
 logger = logging.getLogger(__name__)
 
 
@@ -777,8 +783,11 @@ def _init_threats(self):
         self._add_threats()
 
     def _add_threats(self):
-        with open(self.threatsFile, "r", encoding="utf8") as threat_file:
-            threats_json = json.load(threat_file)
+        try:
+            with open(self.threatsFile, "r", encoding="utf8") as threat_file:
+                threats_json = json.load(threat_file)
+        except (FileNotFoundError, PermissionError, IsADirectoryError) as e:
+            raise UIError(e, f"Failed while trying to open the the threat file ({self.threatsFile}).")
 
         for i in threats_json:
             TM._threats.append(Threat(**i))
@@ -1000,8 +1009,11 @@ def seq(self):
         )
 
     def report(self, template_path):
-        with open(template_path) as file:
-            template = file.read()
+        try:
+            with open(template_path) as file:
+                template = file.read()
+        except (FileNotFoundError, PermissionError, IsADirectoryError) as e:
+            raise UIError(e, f"Failed while trying to open the report template file ({template_path}).")
 
         threats = encode_threat_data(TM._threats)
         findings = encode_threat_data(self.findings)
@@ -1027,6 +1039,15 @@ def report(self, template_path):
         return self._sf.format(template, **data)
 
     def process(self):
+        try:
+            self._process()
+        except UIError as e:
+            print("Failed to complete requested command!")
+            print(f"   {e.context}")
+            print(f"   {e.error}")
+            sys.exit(127)
+
+    def _process(self):
         self.check()
         result = get_args()
         logging.basicConfig(level=logging.INFO, format="%(levelname)s: %(message)s")
@@ -1055,8 +1076,11 @@ def process(self):
             self.sqlDump(result.sqldump)
 
         if result.json:
-            with open(result.json, "w", encoding="utf8") as f:
-                json.dump(self, f, default=to_serializable)
+            try:
+                with open(result.json, "w", encoding="utf8") as f:
+                    json.dump(self, f, default=to_serializable)
+            except (FileExistsError, PermissionError, IsADirectoryError) as e:
+                raise UIError(e, f"Failed while trying to write to the result file ({result.json})")
 
         if result.report is not None:
             print(self.report(result.report))

tests/test_private_func.py

@@ -12,6 +12,7 @@
     Process,
     Server,
     Threat,
+    UIError,
 )
 
 
@@ -46,10 +47,10 @@ def test_kwargs(self):
     def test_load_threats(self):
         tm = TM("TM")
         self.assertNotEqual(len(TM._threats), 0)
-        with self.assertRaises(FileNotFoundError):
+        with self.assertRaises(UIError):
             tm.threatsFile = "threats.json"
 
-        with self.assertRaises(FileNotFoundError):
+        with self.assertRaises(UIError):
             TM("TM", threatsFile="threats.json")
 
     def test_responses(self):