solve assorted issue with newer pylint versions

Includes more use of 'with', adding encodings to open statements
and a couple of issues with parameter renaming.

nominatim/tools/postcodes.py

@@ -36,7 +36,7 @@ class _CountryPostcodesCollector:
 
     def __init__(self, country):
         self.country = country
-        self.collected = dict()
+        self.collected = {}
 
 
     def add(self, postcode, x, y):
@@ -140,7 +140,7 @@ class _CountryPostcodesCollector:
 
         if fname.is_file():
             LOG.info("Using external postcode file '%s'.", fname)
-            return open(fname, 'r')
+            return open(fname, 'r', encoding='utf-8')
 
         fname = project_dir / f'{self.country}_postcodes.csv.gz'
 

nominatim/tools/special_phrases/sp_csv_loader.py

@@ -39,8 +39,8 @@ class SPCsvLoader(Iterator):
         """
         phrases = set()
 
-        with open(self.csv_path) as file:
-            reader = csv.DictReader(file, delimiter=',')
+        with open(self.csv_path, encoding='utf-8') as fd:
+            reader = csv.DictReader(fd, delimiter=',')
             for row in reader:
                 phrases.add(
                     SpecialPhrase(row['phrase'], row['class'], row['type'], row['operator'])