fix : error_test.py fixed.

test/error_test.py

@@ -7,18 +7,20 @@
 Traceback (most recent call last):
         ...
 samila.errors.samilaDataError: Provided data file is not supported. It should be either file or io.IOBase.
->>> with open('data.json', 'r') as fp:
-...     fp.write('test')
->>> g = GenerativeImage(data="data.json")
+>>> with open('data.json', 'w') as fp:
+...     result = fp.write('test')
+>>> g = GenerativeImage(data=open("data.json", 'r'))
+Traceback (most recent call last):
         ...
 samila.errors.samilaDataError: Provided data format is wrong. It should be in JSON format including data1 and data2 fields.
 >>> g = GenerativeImage(lambda x,y: 0, lambda x,y: 0)
 >>> g.generate(step=0.1)
->>> g.save_data('data.json')
->>> g = GenerativeImage(data="data.json")
->>> with warns(RuntimeWarning, match='Just data is provided you can't use generate function.'):
+>>> result = g.save_data('data.json')
+>>> with warns(RuntimeWarning, match="Just data is provided you can't use generate function."):
 ...     g = GenerativeImage(data=open('data.json', 'r'))
 >>> g.generate()
+Traceback (most recent call last):
+        ...
 samila.errors.samilaGenerateError: At least one of the given functions are None.
 >>> os.remove('data.json')
 """