Fix small errors for the tests to be compatible with V3

1) Sanity/test_smart_card_detection.py::test_pam_services_config: added
   new line at the end on /etc/pam.d/pam_cert_service
2) Sanity/test_sssd_conf.py::test_matchrule_defined_for_other_user: fix
   the way it replaces certmap/shadowutils section

Sanity/test_smart_card_detection.py

@@ -1,5 +1,6 @@
 import pytest
-
+from time import sleep
+import pexpect
 
 def test_modutil_token_info(local_user, root_shell):
     """Check that p11-kit module shows smart card information with modutil
@@ -17,7 +18,7 @@ def test_pam_services_config(local_user, root_shell, sssd):
     works as expected for smart card authentication.
     GitHub issue: https://github.com/SSSD/sssd/issues/3967"""
     with open("/etc/pam.d/pam_cert_service", "w") as f:
-        f.write("auth\trequired\tpam_sss.so require_cert_auth")
+        f.write("auth\trequired\tpam_sss.so require_cert_auth\n")
     with sssd(section="pam", key="pam_p11_allowed_services", value="-su") as sssd_conf:
         with local_user.card(insert=False) as sc:
             cmd = "sssctl user-checks -a auth -s pam_cert_service " \

Sanity/test_sssd_conf.py

@@ -136,12 +136,13 @@ def test_matchrule_defined_for_other_user(local_user, sssd, user_shell):
               value="<SUBJECT>.*CN=testuser.*") as sssd_file:
         # FIXME: this section should be replaced with library call for removing
         #  the section as soon as this functionality is implemented
-        with sssd_file.path.open("r+") as sources:
-            sourcesdata = sources.read()
-            sourcesdata = sourcesdata.replace(
+        with sssd_file.path.open("r") as fp:
+            new_context = fp.read()
+            new_context = new_context.replace(
                 f'[certmap/shadowutils/{local_user.username}]',
                 '[certmap/shadowutils/testuser]')
-            sources.write(sourcesdata)
+        with sssd_file.path.open("w") as fp:
+            fp.write(new_context)
         run(["systemctl", "restart", "sssd"])
 
         with Authselect(required=False), local_user.card(insert=True):