tests: Add tests for stream IO errors.

tests/io/file1.py

@@ -12,3 +12,35 @@ f = open("io/data/file1",mode="r")
 print(f.readlines())
 f = open("io/data/file1",mode="rb")
 print(f.readlines())
+
+# write() error
+f = open('io/data/file1', 'r')
+try:
+    f.write('x')
+except OSError:
+    print('OSError')
+f.close()
+
+# read(n) error on binary file
+f = open('io/data/file1', 'ab')
+try:
+    f.read(1)
+except OSError:
+    print('OSError')
+f.close()
+
+# read(n) error on text file
+f = open('io/data/file1', 'at')
+try:
+    f.read(1)
+except OSError:
+    print('OSError')
+f.close()
+
+# readall() error (call read() for compat with CPy)
+f = open('io/data/file1', 'ab')
+try:
+    f.read()
+except OSError:
+    print('OSError')
+f.close()

tests/io/file_readinto.py

@@ -5,3 +5,10 @@ print(b)
 f = open("io/data/file2", "rb")
 print(f.readinto(b))
 print(b)
+
+# readinto() on writable file
+f = open('io/data/file1', 'ab')
+try:
+    f.readinto(bytearray(4))
+except OSError:
+    print('OSError')

tests/io/file_readline.py

@@ -4,3 +4,11 @@ print(f.readline(3))
 print(f.readline(4))
 print(f.readline(5))
 print(f.readline())
+
+# readline() on writable file
+f = open('io/data/file1', 'ab')
+try:
+    f.readline()
+except OSError:
+    print('OSError')
+f.close()

tests/io/file_seek.py

@@ -23,3 +23,12 @@ print(f.seek(6))
 print(f.read(5))
 print(f.tell())
 f.close()
+
+# seek closed file
+f = open('io/data/file1', 'r')
+f.close()
+try:
+    f.seek(1)
+except (OSError, ValueError):
+    # CPy raises ValueError, uPy raises OSError
+    print('OSError or ValueError')