src/vs/platform/extensionManagement/node/extensionManagementService.ts/InstallExtensionTask/installExtension
class InstallExtensionTask:	protected async installExtension(installableExtension: InstallableExtension, token: CancellationToken): Promise<ILocalExtension> {
		try {
			const local = await this.unsetUninstalledAndGetLocal(installableExtension.key);
			if (local) {
				return this.extensionsScanner.updateMetadata(local, installableExtension.metadata);
			}
		} catch (e) {
			if (isMacintosh) {
				throw new ExtensionManagementError(nls.localize('quitCode', "Unable to install the extension. Please Quit and Start VS Code before reinstalling."), ExtensionManagementErrorCode.Internal);
			} else {
				throw new ExtensionManagementError(nls.localize('exitCode', "Unable to install the extension. Please Exit and Start VS Code before reinstalling."), ExtensionManagementErrorCode.Internal);
			}
		}
		return this.extract(installableExtension, token);
	}