我遵循Realm Doc来安装Realm，但是当我执行carthage update命令时，它显示了波纹错误：
$ carthage update
*** Fetching realm-cocoa
*** Checking out realm-cocoa at "v4.3.2"
*** xcodebuild output can be found in /var/folders/8d/5bz90qjn3s109w_z32b7x92c0000gn/T/carthage-xcodebuild.crd29f.log
*** Skipped installing realm-cocoa.framework binary due to the error:
"GitHub API request failed: networkError(Error Domain=NSURLErrorDomain Code=-1003 "A server with the specified hostname could not be found." UserInfo={NSUnderlyingError=0x7fb578786990 {Error Domain=kCFErrorDomainCFNetwork Code=-1003 "(null)" UserInfo={_kCFStreamErrorCodeKey=8, _kCFStreamErrorDomainKey=12}}, NSErrorFailingURLStringKey=https://api.github.com/repos/realm/realm-cocoa/releases/tags/v4.3.2?, NSErrorFailingURLKey=https://api.github.com/repos/realm/realm-cocoa/releases/tags/v4.3.2?, _kCFStreamErrorDomainKey=12, _kCFStreamErrorCodeKey=8, NSLocalizedDescription=A server with the specified hostname could not be found.})"
Falling back to building from the source
*** Building scheme "Realm" in Realm.xcworkspace
Build Failed
Task failed with exit code 65:
/usr/bin/xcrun xcodebuild -workspace /Users/tangmonk/Documents/mygit/fojingdaquan/fojingdaquan/Carthage/Checkouts/realm-cocoa/Carthage/Realm.xcworkspace -scheme Realm -configuration Release -derivedDataPath /Users/tangmonk/Library/Caches/org.carthage.CarthageKit/DerivedData/11.3.1_11C504/realm-cocoa/v4.3.2 -sdk iphoneos ONLY_ACTIVE_ARCH=NO CODE_SIGNING_REQUIRED=NO CODE_SIGN_IDENTITY= CARTHAGE=YES archive -archivePath /var/folders/8d/5bz90qjn3s109w_z32b7x92c0000gn/T/realm-cocoa SKIP_INSTALL=YES GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=NO CLANG_ENABLE_CODE_COVERAGE=NO STRIP_INSTALLED_PRODUCT=NO (launched in /Users/tangmonk/Documents/mygit/fojingdaquan/fojingdaquan/Carthage/Checkouts/realm-cocoa)
This usually indicates that project itself failed to compile. Please check the xcodebuild log for more details: /var/folders/8d/5bz90qjn3s109w_z32b7x92c0000gn/T/carthage-xcodebuild.crd29f.log