[ADD] Show error logs when something bad occurs.

latex.py

@@ -24,9 +24,9 @@ def render(user: str, source: str, png: bool = True) -> str:
     tmp.close()
     # Parse our templated file thru' LaTeX and dvipng.
     # TODO: Allow arbitrary DPI and foreground color.
-    ret = subprocess.run(["latex", "-halt-on-error", tmp.name], cwd="/tmp").returncode
-    if ret != 0:
-        raise FileNotFoundError("DVI couldn't be built.")
+    ret = subprocess.run(["latex", "-halt-on-error", tmp.name], cwd="/tmp", capture_output=True)
+    if ret.returncode != 0:
+        raise FileNotFoundError(ret.stdout.decode())
 
     if png:
         print("PNG")

main.py

@@ -42,16 +42,23 @@ async def msg_cb(room: MatrixRoom, event: RoomMessageText) -> None:
         try:
             filename = latex.render("", event.body)
             await send_png(room, filename)
-        except (FileNotFoundError, OSError):
+        except FileNotFoundError as e:
             content = {
                 "msgtype": "m.text",
-                "body": "Couldn't parse LaTeX correctly."
+                "body": f"Couldn't parse LaTeX correctly.\n```{e.args[0]}\n```",
+                "formatted_body": f"Couldn't parse LaTeX correctly.<br><code><pre>{e.args[0]}</pre></code>",
             }
+
             await client.room_send(room.room_id, message_type="m.room.message", content=content)
+        except OSError:
+            content = {
+                "msgtype": "m.text",
+                "body": "???",
+                "formatted_body": "???"
+            }
 
+            await client.room_send(room.room_id, message_type="m.room.message", content=content)
 # Our file callback.
-
-
 async def file_cb(room: MatrixRoom, event: RoomMessageFile) -> None:
     url = event.url
     filename = event.body