pub fn conjure_executable() -> Result<()> {

    let mut cmd = std::process::Command::new("conjure");

    let output = cmd.arg("--version").output()?;

    let stdout = String::from_utf8(output.stdout)?;

    let stderr = String::from_utf8(output.stderr)?;

    if !stderr.is_empty() {

        bail!("'conjure' results in error: ".to_string() + &stderr);

    }

    let first = stdout

        .lines()

        .next()

        .ok_or(anyhow!("Could not read stdout"))?;

    if first != CORRECT_FIRST_LINE {

        let path = std::env::var("PATH")?;

        let paths = std::env::split_paths(&path);

        let num_conjures = paths.filter(|path| path.join("conjure").exists()).count();

        if num_conjures > 1 {

            bail!(

                "Conjure may be present in PATH after a conflicting name. \

            Make sure to prepend the correct path to Conjure to PATH."

            )

            bail!("The correct Conjure executable is not present in PATH.")

    }

    let version_line = stdout

        .lines()

        .nth(1)

        .ok_or(anyhow!("Could not read Conjure's stdout"))?;

    let version = match version_line.strip_prefix("Release version ") {

        Some(v) => Ok(v),

        None => match version_line.strip_prefix("Conjure v") {

            Some(v) => v.split_whitespace().next().ok_or(anyhow!(

                "Could not read Conjure's version from: {}",

                version_line

            )),

            None => Err(anyhow!(

                "Could not read Conjure's version from: {}",

                version_line

            )),

    }?;

    if Versioning::new(version) < Versioning::new(CONJURE_MIN_VERSION) {

        bail!(

            "Conjure version is too old (< {}): {}",

            CONJURE_MIN_VERSION,

            version

        );

    }

    Ok(())

}