Unable to use GPG support on macOS

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issues](https://copyq.readthedocs.io/en/latest/known-issues.html).

**Describe the bug**
I am using CopyQ on macOS Mojave - all is working well, but I want to use the Encryption add-on. I installed copyq using Homebrew, and then installed gnupg through Homebrew also. However on restart of CopyQ, I still see the message telling me to install GPG and restart CopyQ. The documentation details how to install GPG support on Windows and Linux, but I can't find out how to do it on macOS. I have both the gpg and gpg2 binaries available in the shell.

**To Reproduce**
Steps to reproduce the behavior:
1. Install copyq on macOS Mojave using Homebrew
2. Install gnupg package using Homebrew
3. Restart copyq
4. See message asking for GPG to be installed for encryption support.

**Expected behavior**
Successful install of GPG should mean Encryption options become available.

**Version, OS and Environment**
(Get details from `copyq version` command if possible.)
```
CopyQ Clipboard Manager v3.11.1
Qt: 5.13.2
Compiler: GCC
Arch: x86_64-little_endian-lp64
OS: macOS Mojave (10.14)
```

**Additional context**
Add any other context about the problem here.