explicitly use utf-8 encoding, as defined in the standard

src/icartt/dataset.py

@@ -457,7 +457,7 @@ class Dataset:
                 return dmp
 
         if self.inputFhandle.closed:
-            self.inputFhandle = open(self.inputFhandle.name)
+            self.inputFhandle = open(self.inputFhandle.name, encoding='utf-8')
 
         try:
             f = FilehandleWithLinecounter(self.inputFhandle, splitChar)
@@ -663,7 +663,7 @@ class Dataset:
     def readData(self, splitChar=","):
         """Read ICARTT data (from file)"""
         if self.inputFhandle.closed:
-            self.inputFhandle = open(self.inputFhandle.name)
+            self.inputFhandle = open(self.inputFhandle.name, encoding='utf-8')
 
         try:
             nul = [self.inputFhandle.readline() for i in range(self.nHeaderFile)]
@@ -906,11 +906,11 @@ class Dataset:
         # read data if f is not None
         if f is not None:
             if isinstance(f, (str, pathlib.Path)):
-                self.inputFhandle = open(f, "r")
+                self.inputFhandle = open(f, "r", encoding='utf-8')
             else:
                 self.inputFhandle = f
 
             self.readHeader(splitChar)
             if loadData:
                 self.endDefineMode()
-                self.readData(splitChar)
+                self.readData(splitChar)
\ No newline at end of file