transport: print reader device/number on init

When we initialize the reader, we currently tell only which type of
interface we are using, but we do not print the reader number or the
device path.

Let's extend the messages so that the path is printed. To prevent
problems with integration-tests, let's also add an environment variable
that we can use to detect when pySim runs inside a integration-test.

Related: OS#6210
Change-Id: Ibe296d51885b1ef5f9c9ecaf1d28da52014dcc4b

pySim/transport/serial.py

@@ -18,7 +18,7 @@
 
 import serial
 import time
-import os.path
+import os
 import argparse
 from typing import Optional
 
@@ -33,7 +33,10 @@ class SerialSimLink(LinkBase):
     def __init__(self, device: str = '/dev/ttyUSB0', baudrate: int = 9600, rst: str = '-rts',
                  debug: bool = False, **kwargs):
         super().__init__(**kwargs)
-        print("Using serial reader interface")
+        if os.environ.get('PYSIM_INTEGRATION_TEST') == "1":
+            print("Using serial reader interface")
+        else:
+            print("Using serial reader interface at port %s" % device)
         if not os.path.exists(device):
             raise ValueError("device file %s does not exist -- abort" % device)
         self._sl = serial.Serial(