Command aptly mirror drop with system tests.

system/t04_mirror/DropMirror1Test_gold

@@ -0,0 +1 @@
+Mirror `mirror1` has been removed.

system/t04_mirror/DropMirror1Test_mirror_show

@@ -0,0 +1 @@
+ERROR: unable to show: mirror with name mirror1 not found

system/t04_mirror/DropMirror2Test_gold

@@ -0,0 +1,3 @@
+Mirror `wheezy-main` was used to create following snapshots:
+ * [wheez]: Snapshot from mirror [wheezy-main]: http://mirror.yandex.ru/debian/ wheezy
+ERROR: won't delete mirror with snapshots, use --force to override

system/t04_mirror/DropMirror3Test_gold

@@ -0,0 +1 @@
+Mirror `wheezy-main` has been removed.

system/t04_mirror/DropMirror4Test_gold

@@ -0,0 +1 @@
+ERROR: unable to drop: mirror with name mirror1 not found

system/t04_mirror/__init__.py

@@ -6,3 +6,4 @@ from .create import *
 from .show import *
 from .list import *
 from .update import *
+from .drop import *

system/t04_mirror/drop.py

@@ -0,0 +1,46 @@
+from lib import BaseTest
+
+
+class DropMirror1Test(BaseTest):
+    """
+    drop mirror: regular list
+    """
+    fixtureCmds = [
+        "aptly mirror create mirror1 http://mirror.yandex.ru/debian/ wheezy",
+    ]
+    runCmd = "aptly mirror drop mirror1"
+
+    def check(self):
+        self.check_output()
+        self.check_cmd_output("aptly mirror show mirror1", "mirror_show", expected_code=1)
+
+
+class DropMirror2Test(BaseTest):
+    """
+    drop mirror: in use by snapshots
+    """
+    fixtureDB = True
+    fixtureCmds = [
+        "aptly snapshot create wheez from mirror wheezy-main"
+    ]
+    runCmd = "aptly mirror drop wheezy-main"
+    expectedCode = 1
+
+
+class DropMirror3Test(BaseTest):
+    """
+    drop mirror: force
+    """
+    fixtureDB = True
+    fixtureCmds = [
+        "aptly snapshot create wheez from mirror wheezy-main"
+    ]
+    runCmd = "aptly mirror drop --force wheezy-main"
+
+
+class DropMirror4Test(BaseTest):
+    """
+    drop mirror: no such mirror
+    """
+    runCmd = "aptly mirror drop mirror1"
+    expectedCode = 1