Fix some pylint errors

diofant/printing/dot.py

@@ -1,7 +1,7 @@
 from ..core import Basic, Expr
 
 
-__all__ = 'dotprint'
+__all__ = 'dotprint',
 
 default_styles = [(Basic, {'color': 'blue', 'shape': 'ellipse'}),
                   (Expr,  {'color': 'black'})]

diofant/tests/core/test_args.py

@@ -3,7 +3,6 @@
 # NOTE: keep tests sorted by (module, class name) key.
 
 import inspect
-import io
 import os
 import re
 import warnings
@@ -178,7 +177,7 @@ def test_all_classes_are_tested():
             if not file.endswith('.py'):
                 continue
 
-            with io.open(os.path.join(root, file), 'r', encoding='utf-8') as f:
+            with open(os.path.join(root, file), encoding='utf-8') as f:
                 text = f.read()
 
             submodule = module + '.' + file[:-3]

diofant/tests/external/test_autowrap.py

@@ -115,7 +115,7 @@ def runtest_autowrap_helpers(language, backend):
 
     for file in os.listdir(tmp):
         if file.startswith('wrapped_code_') and file.endswith('.c'):
-            fil = open(tmp + '/' + file)
+            fil = open(tmp + '/' + file, encoding='utf-8')
             assert fil.read() == ('/******************************************************************************\n'
                                   ' *' + ('Code generated with diofant ' + diofant.__version__).center(76) + '*\n'
                                   ' *                                                                            *\n'

diofant/tests/external/test_codegen.py

@@ -120,7 +120,7 @@
 
 def try_run(commands):
     """Run a series of commands and only return True if all ran fine."""
-    null = open(os.devnull, 'w')
+    null = open(os.devnull, 'w', encoding='utf-8')
     for command in commands:
         retcode = subprocess.call(command, stdout=null, shell=True,
                                   stderr=subprocess.STDOUT)
@@ -185,7 +185,7 @@ def run_test(label, routines, numerical_tests, language, commands, friendly=True
         raise NotImplementedError(
             f'FIXME: filename extension unknown for language: {language}')
 
-    with open(f_name, 'w') as f:
+    with open(f_name, 'w', encoding='utf-8') as f:
         f.write(
             main_template[language] % {'statements': ''.join(test_strings)})
 

diofant/tests/logic/test_dimacs.py

@@ -17,7 +17,7 @@
 def load_file(location):
     """Loads a boolean expression from a file."""
     location = os.path.dirname(__file__) + '/' + location
-    with open(location) as f:
+    with open(location, encoding='utf-8') as f:
         s = f.read()
 
     return load(s)

diofant/tests/solvers/test_diophantine.py

@@ -871,7 +871,7 @@ def test_sum_of_squares_powers():
     assert list(sum_of_powers(5, 1, 2, True)) == [(0, 5), (1, 4), (2, 3)]
     assert list(sum_of_powers(6, 2, 2)) == []
     assert list(sum_of_powers(3**5, 3, 1)) == []
-    assert list(sum_of_powers(3**6, 3, 1)) == [(9,)] and (9**3 == 3**6)
+    assert list(sum_of_powers(3**6, 3, 1)) == [(9,)]
     assert list(sum_of_powers(2**1000, 5, 2)) == []
 
 

diofant/utilities/autowrap.py

@@ -167,7 +167,7 @@ def _prepare_files(self, routine):
         return
 
     def _generate_code(self, routine, helpers):
-        with open(f'{self.module_name}.py', 'w') as f:
+        with open(f'{self.module_name}.py', 'w', encoding='utf-8') as f:
             printed = ', '.join(
                 [str(res.expr) for res in routine.result_variables])
             # convert OutputArguments to return value like f2py
@@ -239,7 +239,7 @@ def _prepare_files(self, routine):
         codefilename = f'{self.filename}.{self.generator.code_extension}'
 
         # pyx
-        with open(pyxfilename, 'w') as f:
+        with open(pyxfilename, 'w', encoding='utf-8') as f:
             self.dump_pyx([routine], f, self.filename)
 
         # setup.py
@@ -250,7 +250,7 @@ def _prepare_files(self, routine):
         else:
             np_import = ''
             np_includes = ''
-        with open('setup.py', 'w') as f:
+        with open('setup.py', 'w', encoding='utf-8') as f:
             f.write(self.setup_template.format(ext_args=', '.join(ext_args),
                                                np_import=np_import,
                                                np_includes=np_includes))
@@ -651,11 +651,11 @@ def _prepare_files(self, routine):
 
         # C
         codefilename = self.module_name + '.c'
-        with open(codefilename, 'w') as f:
+        with open(codefilename, 'w', encoding='utf-8') as f:
             self.dump_c([routine], f, self.filename)
 
         # setup.py
-        with open('setup.py', 'w') as f:
+        with open('setup.py', 'w', encoding='utf-8') as f:
             self.dump_setup(f)
 
     @classmethod

diofant/utilities/codegen.py

@@ -663,7 +663,7 @@ def write(self, routines, prefix, to_files=False, header=True, empty=True):
         if to_files:
             for dump_fn in self.dump_fns:
                 filename = f'{prefix}.{dump_fn.extension}'
-                with open(filename, 'w') as f:
+                with open(filename, 'w', encoding='utf-8') as f:
                     dump_fn(self, routines, f, prefix, header, empty)
         else:
             result = []