Try to fix capsys issue with Python 3.8

gns3server/version.py

@@ -31,7 +31,7 @@ if "dev" in __version__:
         import os
         import subprocess
         if os.path.exists(os.path.join(os.path.dirname(os.path.abspath(__file__)), "..", ".git")):
-            r = subprocess.check_output(["git", "rev-parse", "--short", "HEAD"]).decode().strip("\n")
+            r = subprocess.check_output(["git", "rev-parse", "--short", "HEAD"]).decode().strip()
             __version__ += "-" + r
     except Exception as e:
         print(e)