Add option to remove lines from a file

config_replace_variables() can now also remove lines from a file.

Related: https://pagure.io/freeipa/issue/7860
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

ipapython/ipautil.py

@@ -1104,14 +1104,17 @@ def reverse_record_exists(ip_address):
     return True
 
 
-def config_replace_variables(filepath, replacevars=dict(), appendvars=dict()):
+def config_replace_variables(filepath, replacevars=dict(), appendvars=dict(),
+                             removevars=None):
     """
     Take a key=value based configuration file, and write new version
-    with certain values replaced or appended
+    with certain values replaced, appended, or removed.
 
     All (key,value) pairs from replacevars and appendvars that were not found
     in the configuration file, will be added there.
 
+    All entries in set removevars are removed.
+
     It is responsibility of a caller to ensure that replacevars and
     appendvars do not overlap.
 
@@ -1153,7 +1156,11 @@ $)''', re.VERBOSE)
                             elif value.find(appendvars[option]) == -1:
                                 new_line = u"%s=%s %s\n" % (option, value, appendvars[option])
                             old_values[option] = value
-                new_config.write(new_line)
+                        if removevars and option in removevars:
+                            old_values[option] = value
+                            new_line = None
+                if new_line is not None:
+                    new_config.write(new_line)
         # Now add all options from replacevars and appendvars that were not found in the file
         new_vars = replacevars.copy()
         new_vars.update(appendvars)