With the recent version vCenter 7.0.0b there seems still being an issue when having HTTP / HTTPS proxy configured and trying to import an OVA / OVF.
This is the error message you will see most likely:
Failed to deploy OVF package. ThrowableProxy.cause A general system error occurred: Transfer failed: Server not trusted: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target, note that HTTP/s proxy is configured for the transfer.
A quick workaround is to disable Proxy via VAMI and only enable it when you need id to download updates via Lifecycle Manager or for vCenter updates.
Most of the time is because NO_PROXY is not set properly
NO_PROXY="localhost, 127.0.0.1, .*.vmware.com, 192.168.1.0/24"
Update, there is a KB out at VMware that you need to specify NO_PROXY according to your environment to get this working again.