Fixed exception when log file not available

src/trader.py

@@ -5,6 +5,7 @@ from .data import log
 
 
 def read_log(logfile: str, app: gui.Gui) -> None:
+    try:
         logfile = open(logfile, 'r', encoding='utf8')
         loglines = follow(logfile)
         for line in loglines:
@@ -13,6 +14,8 @@ def read_log(logfile: str, app: gui.Gui) -> None:
             if message and message.trade and message.to_from == 'From':
                 log.debug(message.trade)
                 app.add_tab(30, message)
+    except IOError:
+        log.error(f'Error opening log file {logfile}.')
 
 
 def follow(thefile: str):