the ci is always failed: continuous-integration/appveyor/pr — AppVeyor build failed

[xiaods]

Hi there,

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System information

Geth version: geth version
OS & Version: Windows/Linux/OSX
Commit hash : (if develop)

Expected behaviour

AppVeyor build can pass

Actual behaviour

AppVeyor build failed

Steps to reproduce the behaviour

submit a pr and testing it. e.g:
https://ci.appveyor.com/project/ethereum/go-ethereum/builds/21662297

Backtrace

github.com/ethereum/go-ethereum/cmd/swarm/swarm-smoke	[no test files]
--- FAIL: TestSnapshotCreate (0.00s)
    --- FAIL: TestSnapshotCreate/defaults (0.36s)
        test_cmd.go:250: (stderr) open C:\gopath\src\github.com\ethereum\go-ethereum\cmd\swarm\swarm-snapshot/C:\Users\appveyor\AppData\Local\Temp\1\swarm-snapshot233205527: The filename, directory name, or volume label syntax is incorrect.
        create_test.go:81: command exit code 1, expected 0
    --- FAIL: TestSnapshotCreate/services (0.39s)
        test_cmd.go:250: (stderr) open C:\gopath\src\github.com\ethereum\go-ethereum\cmd\swarm\swarm-snapshot/C:\Users\appveyor\AppData\Local\Temp\1\swarm-snapshot594488714: The filename, directory name, or volume label syntax is incorrect.
        create_test.go:81: command exit code 1, expected 0
    --- FAIL: TestSnapshotCreate/more_nodes (0.35s)
        test_cmd.go:250: (stderr) open C:\gopath\src\github.com\ethereum\go-ethereum\cmd\swarm\swarm-snapshot/C:\Users\appveyor\AppData\Local\Temp\1\swarm-snapshot724447073: The filename, directory name, or volume label syntax is incorrect.
        create_test.go:81: command exit code 1, expected 0
    --- FAIL: TestSnapshotCreate/services_with_bzz (0.39s)
        test_cmd.go:250: (stderr) open C:\gopath\src\github.com\ethereum\go-ethereum\cmd\swarm\swarm-snapshot/C:\Users\appveyor\AppData\Local\Temp\1\swarm-snapshot339131212: The filename, directory name, or volume label syntax is incorrect.
        create_test.go:81: command exit code 1, expected 0
FAIL
coverage: 0.0% of statements
FAIL	github.com/ethereum/go-ethereum/cmd/swarm/swarm-snapshot	1.008s