Added bad-format-string, consider-using-sys-exit, global-statement examples

doc/data/messages/b/bad-format-string/bad.py

@@ -0,0 +1 @@
+print('{a[0] + a[1]}'.format(a=[0, 1])) # [bad-format-string]

doc/data/messages/b/bad-format-string/good.py

@@ -0,0 +1 @@
+print('{a[0]} + {a[1]}'.format(a=[0, 1]))

doc/data/messages/b/bad-format-string/related.rst

@@ -0,0 +1,2 @@
+- `Format String Syntax <https://docs.python.org/3/library/string.html#formatstrings>`_
+- `PyFormat <https://pyformat.info/>`_

doc/data/messages/c/consider-using-sys-exit/bad.py

@@ -0,0 +1,4 @@
+if __name__ == '__main__':
+    user = input('Enter user name: ')
+    print(f'Hello, {user}')
+    exit(0) # [consider-using-sys-exit]

doc/data/messages/c/consider-using-sys-exit/good.py

@@ -0,0 +1,6 @@
+import sys
+
+if __name__ == '__main__':
+    user = input('Enter user name: ')
+    print(f'Hello, {user}')
+    sys.exit(0)

doc/data/messages/g/global-statement/bad.py

@@ -0,0 +1,9 @@
+var = 1
+
+def foo():
+    global var # [global-statement]
+    var = 10
+    print(var)
+
+foo()
+print(var)

doc/data/messages/g/global-statement/good.py

@@ -0,0 +1,8 @@
+var = 1
+
+def foo(x):
+    print(var)
+    return 10
+
+var = foo()
+print(var)