More helpful error message when IP does not resolve for OLED screen (#541)

* More helpful error message

* Remove confusing fallback IP

* Tweak message

src/oled_monitor/pi_cmds.py

@@ -14,7 +14,7 @@ def get_ip_and_host():
         sock.connect(('10.255.255.255', 1))
         ip_addr = sock.getsockname()[0]
     except Exception:
-        ip_addr = '127.0.0.1'
+        ip_addr = False
     finally:
         sock.close()
     return ip_addr, host

src/oled_monitor/rascsi_oled_monitor.py

@@ -161,7 +161,11 @@ def formatted_output():
     else:
         output.append("No image mounted!")
 
-    output.append(f"IP {IP_ADDR} - {HOSTNAME}")
+    if IP_ADDR:
+        output.append(f"IP {IP_ADDR} - {HOSTNAME}")
+    else:
+        output.append("RaSCSI has no IP address")
+        output.append("Check network connection")
     return output